In SC the signs say "ALL TRUCKS". I stopped in yesterday to ask a few questions and got the answer that if your GVWR is over 10,001 then you better pull in.
This is what I get when I read the CFR on the subject. I'm not a lawyer though... Add to that, sometimes state agencies are sent out to enforce federal rules, sometimes state rules, sometimes rules specific to specific classes of vehicles, and they won't touch the rest. When IRS set up here a couple years ago, they did not have ANY special signage, but they wanted every diesel truck to pull in, and went after the ones that did not, took their sample and left stern warning that even pickups (well, some pickups) have to pull in any time it says "all trucks"...
I have a philosiphy on this-
The law is the law, period. You may be right. But the fight may be more costly in both time and money than the fine is.
Option one- You pull in, and they are slightly annoyed (but probably not at all annoyed) that you pulled in based on the "all trucks" thing and wasted their time since the inspection of the day is S-cam adjustment or something similar.
In the worst case they are slightly annoyed as they explain to you that you do not need to stop for them and you should be on your way...
Option two- You drive by, and one of them gets a whim to find out who you are and what you are up to. Even though you didn't qualify for whatever they're inspecting for, you are now in the position of explaining to a ticked off LEO who just chased you down that his inspection doesn't pertain to you and he should be on his way...
There is only one law, and therefore only one right answer to any given situation, but I can see two distinctly different outcomes here...