LA is record store heaven.
Amoeba is probably the largest store in the country- best for newer vinyl in all genres, but have some used stuff too. Size of a Macys.
Record Surplus in Santa Monica has a large selection of mostly older, used stuff at good prices but some aren't best quality
Quite a few vinyl boutiques have been opened up in Echo Park/Silver Lake (read: hipster) areas...Origami, Wombleton, etc. Once it cools down, intend to visit a couple of them. I've heard they are more curated collections and charge a premium.