What doghead said, but...
If you are looking at Ft. Meade, yes, you can drive it off, if it's drivable. You'll need to contact your DMV to get a temporary plate.
JUST BECAUSE IT IS LISTED AS "DROVE ONTO LOT" DOES NOT MEAN THAT IT IS IN SAFE OR RELIABLE DRIVING CONDITION!!!
For example, my recent M1008 purchase was listed as "drove onto lot", but I wound up towing it home. It would not shift into 2nd gear. That ain't gonna work on the highway! Then, while I was putting around, it munched the 2nd alternator belt. I had to rent a trailer and go back another day.
I think "drove onto lot" means it was driven off of a flatbed and they were able to park it in their lot. It does NOT mean it was test driven and it does NOT mean it is highway ready!
No, no weekends. You'll have to take a day off work.
Remember that it's a military installation. You'll have to pass through inspection, and you WILL have to have current registration, driver license, and proof of insurance. The inspection is no big deal - they'll ask you to open your doors and all compartments (glove box, hood, trunk, etc.) and they'll peek in.
Paperwork is easy. You print out a copy of your invoice, which you can download off the site when you log into your account. Take it with you. You'll sign that you have received the material.
Once you get home, you go onto the GL website and there's info on getting a title. There's a form to fill out. After a couple of weeks, you'll get a clear Arizona title in the mail, and then you can go register your truck.
On the other hand, I just picked up some non-vehicle stuff at GL's Norfolk location, and it's NEXT to the navy base, but not on it. No inspection, no security, just drive up, load up, and leave.
Anyway, back to what doghead said. Call. The phone number for the installation will be on your paid invoice. Remember that they are not heavily staffed, and they may be out on the lot and not hear your call. If you are one of those people that hates voicemail, get over it. Leave a message or lose out.