In reply to BoredTired&Lazy:
J Tree is closer to LA and will very likely have better weather. Should have no problem meeting people at Hidden Valley campground, or the boulders. I imagine you can hire pads at Nomad Ventures in J Tree. Not sure what the scene is like in the Valley around then, but probably pretty quiet. Obviously Yosemite is more spectacular, but J Tree is also cool and you can do some hikes etc too. Doing both is possible, but quite a bit of driving, and climbing in Yosemite could be more hit and miss, although you could still probably hike / look around. If its just for a few days and you want to boulder, I'd go to J Tree.