Joshua Tree is an easy weekend trip, about 3 hours drive. Best season is Feb-April (or October-Dec.). Granite, beautiful area, great single pitch trad., some good bouldering, a little hard-ish sport and a traditional venue for Los Angelinos to go wild in the desert. The main local areas is Mt Woodson, a pile of granite boulders, which has some very trad. crack-climbing and some bouldering. There are lots of other smaller local cragging and bouldering areas, mostly granite. You could do a whole lot worse.
<edit> There is also the granite trad. at Idyllwild, Tahquitz and Suicide Rocks, about 2 hours drive, but this is in condition later in the year so not sure if this will be suitable for when you'll be there.
Bishop and Las Vegas - Red Rocks - are rather further (5-6 hours drive) but not impossible for a long weekend. World-class bouldering and great trad. / good sport / limited bouldering respectively.
I've only spent 4 days in San Diego and it seemed pleasant but a little dull ... perhaps I missed the interesting bits.