I went to Silver Lake Dunes back in 1997 with my Cousin, we towed 2 sand rails out there with his dually Chevy, the truck got stuck while we were unloading the rails and stayed stuck for 3 days while we played. It took 5 hours of digging, a 12500lb winch, a sand anchor, and 2 sand jacks to get it out but we had a blast.
Dont know if they still let ya camp out in designated areas of the dunes but back then they did.
A great place, I'd like to go back someday.