When I was stationed in Twentynine Palms, we use to go hiking in what was then Joshua Tree National Monument. At that time (early 80's), there were no real trailer sites. The house my ex and I were renting was just about ˝ mile from the back edge of the park. It was great to just wander over and enjoy the park. I keep wanting to go back, but I keep finding other spots I want to see.
... A good first world problem.
Enjoy Joshua Tree, it's certainly one of our more hidden gems (along with Capital Reef).