The biggest independent bridal shop in SoCal is Mon Ami in Costa Mesa. However, they are way overpriced (think of them as Kleinfeld West), and I'm not entirely sure they carry plus sizes in the store to try on.
I compiled a list of some of the bridal shops in SoCal I checked out when I was on my 60+ dress tour - I'll post it here and maybe you could call the ones near you to see about sizing.
But I agree with turtle51 - Alfred Angelo is probably your best bet for size variety. Some of the boutiques I went to - especially the ones in the San Gabriel Valley - didn't stock any size bigger than a (sized-down, wedding version of a) 6!

However, those shops, especially in Temple City, can order most name-brand dresses in any size at great prices. So if you already knew what you wanted, you could get, say, a Maggie Sottero for $400.
Camarillo Bridal
(805) 389-1515
Tuesday-Fri: 11-6
Sat:10-5
Closed Sun
Lucys Bridal
9224 Las Tunas Dr
Temple City, CA 91780
626-287-1112
Bridal Elegance
22223 Palos Verdes Blvd
Torrance, CA 90505
(310) 406-3917
Tues-Wed: 10-5
Thurs: 11-7
Fri-Sat:10-6
Sun & Mon appt only
La Soie
19800 Hawthorne Blvd 90503
310-921-1198
M-F: 11-7
Sat: 10-7
Sun: 10-6
Mariposa Boutique
316 N. Anaheim Blvd.
Anaheim, CA 92805
Main 714.776.6881
http://www.mariposabride.com/
Also, Google is a great resource - and Yelp! There may be dress-shop reviews for your area on
www.yelp.com.
