hehe... just happened to be looking through norcal threads...
I have been there many times for camping, rock climbing and hiking. Camping is a large temperature swing so winds are high and unstable/tall tents can get knocked down. Rock climbing is different than granite. It is sandstone that grips good but crumbles under your feet. Crack climbs are easier, slabs are more difficult. Beware of the long hike to lost Oasis... not much there, the Oasis at the beginning of the hike is much better.
I went through there once for 4x4, here is a small write up.
The loop to the top of Geology Trail is pretty easy. Once you head into Berdoo canyon I myself didn't think I would be able to come back up with my truck. But going down I would do it again. It is a long loop taking Rt 10 to Rt 62 to get back up to the top of Joshua Tree.