Slapyo said:http://www.bcmcmustang.homestead.com/
the beach cities mustang club has some car shows and cruises as well. i've been to a few of them.
if you are looking for shows in general, no mustang specific, then a good one to check out is every saturday morning in huntington beach.
http://www.donutderelicts.com
it's at the corner of Adams and Magnolia in huntington beach. lots of different cars show up to it, including quite a few mustangs. sometimes this guy shows up in his f50.