I generally wave to fellow campers when not on the highway, usually smaller roads. We live in the middle of 4 campgrounds and we often have our MH out for the day between day trips to the local lake or to Jekyll Island and I always wave to fellow campers. I rarely get a response.
I know waving is big in the Jeep and Motorcycle communities as well as the road bicycle communities. It doesn't seem to translate to the RV community. I also wave and/or say hello when in a campground. Over the years I've gotten less and less return hellos or waves. It seems the seasonal crowd is more friendly than the weekend warriors.
-Michael