I think if you come to SoCal you come for either great Mexican or any type of Asian food (especially Thai, Korean, Vietnamese Filipino, etc.). We certainly have food from around the globe here, and it's pretty assured you can find a spot or two that makes whatever ethnic cuisine you want, but the ones I mentioned burn the brightest here. Just my opinion, of course.
ETA: as far as mom and pop shops go, I dunno man. I think there are a ton around if you look. My favorite Vietnamese, Chinese, and burger joints are all small hole-in-the-wall type places. All three are pretty damn small now that I think about it.