I strongly recommend San Fran. I have been 6 times now. It is my favourite city. I have also been to LA and Palm Springs, but I think San Fran is the most beautiful and so interesting. It has so much history and cool things to see and do.
Alcatraz, Chinatown, Fishermans Wharf, Steep windy hills, Golden Gate, Marin County near by, UC-Berkeley, great downtown, trolley tours etc...
I was just there on the weekend actually to watch the UBC - Cal rugby games that I used to play in.