On a "primitive" campsite, I would think that you could do this with most State Parks / State Recreational areas without any problems. You don't have to tell anyone you are NOT setting up a tent. You "could" be sleeping on the ground in a sleeping bag with no cover! (Primitive ... no water, sewer, or electric hook-ups camp sites). Many times, I've seen tent campers set up camp when they first arrive, then about midnight, fold everything up and go home. I've never understood why anyone would do this, but I've seen it several times in Indiana State Parks. I understand breaking camp and going home when it begins to rain though, seen this more times than I can remember.