I know I'm raising this one from the long dead, but somebody PM'd me about the trip. Long story short, I did it. I had zero problems. I made new friends and experienced hundreds of different cultures. I got invited lots of cool places, learned a lot about how international politics really work, and would do it again in something smaller. I had zero technology for the trip, did it all with a compass because my laptop took a flying leap off my passenger seat when I hit a speedbump in Mexico at 45MPH. Whoops. When I got to Panama, I traded the truck to another expat who had an unwanted paraglider. I think it's in Costa Rica now. I never returned to the US, but my film did. If I ever go back I'll develop it. We'll see what life brings.
So here's the story.
I crossed over in Matamoras, Texas. Leaving the US is easy. Border Patrol has been supplanted by the same blue shirted people you see at airports, and they did nothing except wave me goodbye as I left. Americans have the right to leave the country at will, something you grow to appreciate when you find out that many people have to ask permission to leave their country. Mexican customs was well organized and safe. The whole compound was guarded by regular army troops, and they did a good job of keeping thieves and hustlers away. The procedure at every border is exactly the same. 1. Declare your vehicle to customs. 2. Buy any insurance if necessary. 3. Get yourself stamped in. On leaving: 1. Stamp your vehicle out. 2. Stamp yourself out. Mexico demands a $200.00 fee when you enter with a vehicle. This fee is refundable when the vehicle leaves the country. The office is called Banjercito. This is a minor complication, because when you exit Mexico there is no Banjercito office at the border. You have to get it done in Tapachula, if exiting to Guatemala. Their office is not easy to find, and if you don't speak basic Spanish you're going to get frustrated. Also, make sure you tell them you are Transmigrante or you will not be allowed outside the tourist zone. Transmigrante. Remember it. It means that you are exiting Mexico through Guatemala or Belize rather than going north again. If you fail to do this you'll get turned around at the interior checkpoint and have to go back and sort out your visa.
Mexico is a beautiful country. Northern Mexico is scrub desert, with the military everywhere. You'll pass many sleepy villages, modern wind farms, and lots of agave and cactus. It reminds me of the Southwest. Don't believe a word about Cartel violence. It will not affect you. You can't drive anywhere without seeing the military. Military checkpoints are a chance to brush up on your Spanish and negotiate the purchase of any armament you'd like for your journey. Military men are curious and friendly, knowing that a southbound American presents zero threat to Mexican security. They don't expect to be bribed, sometimes want a picture with you, and are exactly what you'd expect a bunch of bored government employees stationed in the middle of nowhere to be like.
Driving in Mexico is dangerous. Roads are bad, do not drive at night. There are no lines, no reflectors, no signs, no lights. Construction is not marked. Landslides are not marked. Speedbumps the size of your refrigerator are not marked. Sinkholes? Not marked. Campesino roadblocks? Not marked. Pile of dead animals in the middle of the road? Not marked. Headlights have two settings: Off and High Beam. You will be blinded by everybody. Mexican drivers are crazy, even by Centroamerican standards. You will be passed on the right by oncoming traffic. I witnessed tractor trailers passing 4 abreast at 60MPH on a 2 lane road uphill around a blind corner with a 2000 foot drop and no guardrail. The reason they were in a hurry? A slow moving cop in a 60's vintage Beetle was failing to make it up the mountain. Many cars have no brake lights. Don't follow too close. All of this stuff happens in the daytime, but at least you can see it coming. Don't drive at night, you won't know what hit you.
Find a hotel early. Mexico doesn't have many of them outside of touristy areas. Start looking at 3 in the afternoon and stay at the first one you see. Hotel signs are not lit at night, so if it gets dark your chances of finding one drop to near zero. This leads to driving at night, which is an established bad behavior.
Southern Mexico starts to look like an equatorial jungle once you pass Mexico City. I bypassed the urban area since I was driving a vehicle that's not city friendly and so can't offer any advice about the metro. I think that southern Mexico is nicer than the northern part. There's more agriculture, and farmers are salt of the earth type people. Local produce is easy to find, and you can expect a bit of travelers diarrhea if you eat it. I contend that it's still healthier than processed food, but to each their own. If you like Tequila, ask around for Contraband. It's the local moonshine, and asking for it will make you instant friends. Mexicans don't dig alcohol taxes any more than their Norteamericano counterparts, and you might get invited to a local party. At the very least you'll sample local flavors and meet interesting people.
Crossing into Guatemala is easy, though the Tapachula crossing can be hectic. Neither border is guarded, so expect to run into every kind of con man. Don't trust anybody unless they're sitting at the immigration office. People yelling or waving badges at you can be run over if they stand in your way. They'll jump out in time. Hit the horn and the gas. They are not affiliated with the border. Real border officials are polite and respectful. They don't expect bribes. Everybody else at the border is the scum of the country. Crossing fees were 41 Quetzales when I crossed, but check for current information. You will not be searched going south. Like in Mexico, nobody cares about rich Americans. Get out of the area quickly, before you get into a bad situation. If you get involved in an altercation, pretend like it didn't happen. Nobody cares. Borders are crazy places.
Guatemala has some of the friendliest people in Central America. The indigenous people put on costumes and dance at every speedbump. If you're entertained, give them some change. 1 Quetzal is sufficient. They also like US money. Campesinos sit outside their houses and wave at vehicles going by. They're just being friendly, give em a honk. Sometimes they put empty 2 liter soda bottles on the end of a stick and wave at you. This is the signal that there's a speedbump nearby. Slow down. Topes (speedbumps) are just as big in Guatemala as they are in Mexico. Guatemala is a cheap country. You can get a hotel for 15-20 Quetzales, and the rooms are clean and modernish. I didn't get any bedbugs in Guatemala. Roaches are everywhere because of the climate and proximity to the sea. A roach in your room does not mean that it's dirty. Just leave the windows open and the lizards will come in at night to eat them. Yum! American food is expensive there. A can of Coke will cost more than a hotel room. Guatemalans are basically honest, but will take your money if you're not familiar with the exchange rate. I was warned by everybody to be careful, but ran into no trouble at all. Stay in hotels with armed security, because thieves will liberate your stuff if you don't watch it. There is a lot of history in Guatemala, and you can spend a lot of time there if you're inclined.
From Guatemala you can either go to Honduras or El Salvador. El Salvador is on the Pan American Highway, while the route through Honduras takes you through the mountains. I went the more direct route through El Salvador. This is the most dangerous country I visited. Getting in and out was uneventful, but driving through made it very clear the impact that MS13 had on the country. There aren't any hotels outside of San Salvador, so if you need to spend the night make sure you stop in the capital to sleep in safety. If you don't, your only lodging options are brothels. Pick a brothel with armed security. MS13 is a very real threat. You don't need to use the services inside the brothel, but you'll be happy for the secure parking. I didn't use the services, so don't ask for a review. The next morning, both my truck and I left unmolested.
Honduras is only 50 miles wide where I crossed, and I checked in and out in a single day. No problems here, though I hear that gang activity is on the rise. If you explore the country, have fun and be careful.
Nicaragua probably has the worst reputation of all Central American countries, but it is a peaceful place. Corruption is high, and you may end up having to bribe your way out of hassle. Never give police your original documents. They'll complain about photocopies, but who cares? Be a dumb gringo. It works. If you're having a good experience with somebody with a badge, be friendly and polite. If they're trying to intimidate you, be friendly, polite, stupid, and don't speak a word of Spanish. Not. A. Word. Don't comply with instructions ever. Doing so reveals that you understand them. But don't drop the smile either. Police officers will eventually go away, frustrated and muttering. Wave goodbye when they do. After all, you don't understand what just happened between you and that nice man. If you don't get involved with uniformed inconveniences, enjoy the hospitality of Nicaragua. Lake Nicaragua is a nice place to visit, and San Juan del Sur is a good place to connect with other gringos and enjoy the beach. Managua is an old city with no organization, signage, or reason to visit. Avoid it if you can. The east coast of Nicaragua is remote, rural, and peaceful. Nobody goes there, so if you'd like to get way off the beaten path there are lots of places to explore. Nicaraguans are very honest people. They will not rob you or shortchange you. They will not charge you a gringo price. I felt very respected by the people there. If you like rum, be sure to buy some Flor de Cana 18 or 21 year while you're in country. You won't regret it.
Crossing into Costa Rica is a hassle on the Nicaraguan side. I actually hired one of the border guides, who summoned about 15 kids to hold my place in the various lines. I encourage you to do the same. I gave the guy my passport and all my vehicle paperwork, which I don't recommend, but it turned out fine anyway. I sat in the shade drinking rum and enjoying a Cuban while my paperwork made the rounds. The only thing I actually had to be present for was the official stamping out of the country. Be aware that they won't accept their own currency for the border fees. They demand US dollars, which can be hard to find if you don't have any. Moneychangers at this border don't always have greenbacks, but will give you a fair rate if they do. Like I said, Nicaraguans are pretty honest.
Costa Rica is a lot more organized. There are no fees, which speeds things up a lot. The border compound is guarded and only licensed vendors are allowed inside. You don't have to watch your stuff too closely. Once you get outside, be careful. Costa Rica is a beautiful country, but they love their petty robbery there. Your chances of being the victim of violent crime hover around zero, but whenever you blink somebody has their hands on your stuff. The Nicoya peninsula is a nice rural place to visit. Be aware that diesel can be tough to find outside of cities. The government controls the margins on fuel, so places without many cars don't get gas stations. There's no money in it. Stay away from Limon, it's a dirty port city with lots of crime and nothing to see. Jaco is a tourist trap, close to the international airport but it's a terrible beach. People only go there for drugs and prostitutes. Manuel Antonio is a very nice beach, but spendy. The interior of the country is agrarian, and if you're tired of the constant humidity you can head to a place like Turrialba or Orosi for a respite from the heat. These places are farming communities, and farmers are decent people. Orosi in particular is an idyllic place.
Heading south into Panama is easy, but dealing with Panamanians is hard. They're still sore about the whole invasion thing. Also they're mad about Noriega. One guy yelled at me about of the School of the Americas. "I'm sorry my country pooped on your country, and had I been president at the time things would have gone down different. Now please sell me diesel." No dice. I finally wised up and bought an Argentine Futbol shirt. I can pass for Argentine, and since Panama doesn't like Futbol much I didn't get involved in a single riot.
Panama City is very cosmopolitan, with a great divide between rich and poor. Don't be out at night, but explore freely during the day. Take a ride on the continents first transcontinental railroad, but don't spend too much time in Colon. It's not safe. Do visit the Miraflores locks and watch some very big ships go through a very famous canal. The supertankers get lifted early in the morning, around 5-7. This is one of the few places in the world it's possible to watch the sun rise over the Atlantic and set on the Pacific on the same day. South of Panama City is a whole lot of nothing. The road ends at the Darien Gap, which is a dangerous place. If you go, bring firearms. The smugglers at the gap don't care much for the military, and there's an ongoing war that neither Panama nor Columbia will admit is happening. If you choose to visit the end of the road at Yavisa, take a bus. Parque Nacional Darien is an amazing place, and I recommend you visit. But hire a guide so that nobody mistakes you for a combatant. It's one of the most unvisited places in the world. See harpy eagles pluck monkeys from treetops, thousands of rare and endangered species, and visit indigenous people who haven't changed their ways for thousands of years. All with the background chorus of occasional automatic weapons chatter. You'll have much better stories for your grandkids than their other relatives.
So that was the trip. Fun times were had, life perspectives were changed, and I never went back to my old life. I did the trip with next to no planning, ~5,000 dollars, and 2 months of spare time. You can too. It's highly recommended.
In summary: people are the same everywhere, borders are a pain, and nobody gives a crap about southbound traffic.