Unfortunately, the card shop in Santa Monica I knew of closed down.
There's Frank and Sons in the City of Industry
Open Wednesdays and Saturday
Jimmys USA in Whittier
Jimmy's USA | Jimmy's USA – All Collectible Show Since 1979
And SouthBay Sportcards
1751 Pacific Coast Highway, Lomita, CA
Really good place and I think they are open 7days a week
Check out this thread, might provide some info on each.
Southern California LCS
The locations listed might be out of your way but Frank and Son is a great spot with plenty of vendors and some pretty good deals.