Being a Nevada native I can tell you that I'm not sure about crashed UFOs and stuff (because I'm not sure that actual UFOs are real, although I'm positive there is some life on one of the infinate number of planets out there.)

I do know that they have signs on the perimiters that say stuff like "Tresspassers will be shot on sight," And these are military signs

Something big goes on there cuz it's way top secret, but I'm guessing we probably test out new advanced military technology or something