In my immediate area, there is only Joann's, so I buy most of my fabric at Michael Levine's, here is their site:http://www.lowpricefabric.com/
I visit their store in downtown LA, in the fabric district, where there are a few blocks of fabric (and bead) stores to visit. Michael Levine's huge!
There is also a Mood in Los Angeles but I don't buy much fabric there. A lot of it is too fancy and expensive for me.http://www.moodfabrics.com/