There are lots of really awesome places to go, but I'm really partial to the Anza Borrego area. There is a really nice little resort in Borrego Springs which you can make your base of operations - out for a couple days, back to the resort for a shower and some margaritas in the hot tub.
If you're middle-aged and creaky like me, that hot tub is a beautiful thing!
It's less than 2 hours east of San Diego, and it's within half a day of Mojave and most of a day to Death Valley.
When they say Harleys are for 1%ers, I don't think they mean guys who sell crank and get in bar fights any more.