I was in SF last week, Amoeba Records in SF is the best record shop i have ever been to.
Take plenty of money i burned through $450 in 5 days on just day to day stuff. I used this to find out about live music
http://www.foopee.com/punk/the-list/by-date.5.html
I was recommended to check out these record shops too, but didn't have time or cash:
Stranded
1 2 3 4 Go
Thrillhouse
Make sure you get some good mexican food while yr there.
Berkeley is pretty nice and worth a visit, Telegraph Ave is a fun street to walk down, there's another slightly smaller branch of Amoeba there too
I've never been to LA but if you can check out the documentary City of Gold about the LA Times food critic Jonathan Gold, he's a former punk rocker from LAs punk golden era, and now he hunts down the tasty and amazing looking global immigrant food symbol guy mentioned