We found this by chance as we were heading to McWilliams for an overnight, but they were full.
On a lark, we saw the sign and decided to take a look. As we SUV camp (and not 4x4) we didn't head a long way in, but discovered numerous locations that were easy to get to, but still secluded.
Very few cars, and a nice getaway. Just be aware there are no open fires, only stoves. But we'll do this regularly when we want to get away from the heat of Vegas.