I moved to vegas from a northern state with tree, etc. I didn't visit Mt Charleston until a couple years after i moved to vegas.

I wish i'd discovered it earlier. Very cool. About 1 hour outside of vegas, the tem drops from 120 to 85 in the summer. Pine trees and mountains everywhere.

Its very much worth the drive if you're in vegas for a week with a rental car and getting bored (or going broke). There is a really cool restaurant/bar up in the mountains. There are cabins up there too but the are pretty pricey and very un-private -- i wouldn't stay there.
Also, there are picnic/state camping up there.

And pretty cool scenic views. I've brought a few ladies up there and they really liked it.

My usual trip: 1 hour there, hiking on one of the cool (usually quiet) nature trails, lunch and a few beers at the restuarant, ice cream, a drive out about 20 min farther to the great scenic look out into the desert (i can't remember the name - ask) and an hour or so back to vegas. A good, cheap way to kill an afternoon after you've lost your a** in the casinos. Also check out Red Rock Canyon if you're looking for nature stuff to do (flip over rocks to find scorpians and stuff)