It's a bit of a drive but Revo Cycles in Dana Point (Orange County) fit me before a test ride. If you want to check them out, talk to Darren. He spent about 30 minutes fitting me before a test ride, and actually let me ride the bike off of the lot in the near by neighborhood. After purchasing the bike, he did a thorough fitting. There should be shops in the LA area willing to do the same, try Bicycle John's.