Drive or walk to Mexico (border city Tijuana) to see quite another world and culture :-). The world biggest border crossing point waits for you! Well, Tijuana is not real Mexico but if you are so close... it's good option to take at least half a day trip across the border.
My top reasons to visit Tijuana:
1. I could say: I was in Mexico :-)
2. Mexican food and drinks :-)
3. inexpensive shopping (souvenirs)
4. it's quite different culture easily to find out of the main tourist district.
Details on my Tijuana, Mexico page here.
San Diego is probably the best place to live at. I've been there quite a few months in 1988/9 and I can't say what is best. Everything is best. The sun, the sea, the restaurants, the people,.......
Go there and see for yourself !!!!!!!!
Fondest memory: Probably the most emotional thing is boarding a tram in the center of San Diego and going down to the mexican boarder, exit the tram, walk over the bridge and you are in a completely different world. This is fascinating.