I went up Thomas Mountain on Monday (Memorial Day) started around noon on the north entrance. Encountered one Jeep that was coming down. YP #1 at bottom had people, YP#2 had people. Every other site was vacant. I don't know if people left early Monday morning or if it wasn't that crowded over the weekend.
I stayed at YP #6. The spur to the top was a little rutted up for my tastes and experience level. #6 was great, flat, spacious. A little bit of trash but I spent about an hour cleaning it up and packed out a lot of broken glass, bottle cpas, random pieces of plastic, spent ammo shells, paper/plastic trash, etc.
Saw maybe 5 vehicles go by the rest of the day. Left Tuesday around noon and didn't see a sole all the way down.
One of the sites at toolbox springs with the vault toilet had a lot of trash but I didn't have time to clean it up. And the vault toilet, eh, what a wreck. Bring our own porta potty if you plan to go there!
Shame people don't leave the place better than they found it.