I have a feeling you'd like Huntington Gardens -- some pics:
Desert garden:
 
Japanese garden:
 
If you're out there, you should make it to the ocean, of course -- Santa Monica is kind of the classic, rather (ahem) touristy, though.  Our favorite beach was in Malibu (!) something about heaven, I'll see if I can find it.  Might be too far for you though.