Listen to UCGal its obvious to me she knows what she is talking about. I too love Philly but I understand it in ways you never will. Its my home town and I have tons of childhood friends I stay in touch with.
The immigrants live of the periphery and alot of what they make is through cash businesses. Tax fraud and getting cash discounts in neighborhood stores is well accepted there. It is a world you know nothing about and could take a beating in.
Chinatown has been there for probably close to 100 years. They live their own sheltered existence in their own world. Many illegal businesses are carried out in the backs of the restaurants and stores you see.
Its not like SD where races and cultures mix more freely. The fact that we dont have a Chinatown in SD is a good thing in my mind, its speaks to an inclusionary society unlike the exclusionary society in Philly where each ethniciaty stays far more segregated.
There is far more opportunity in CA for young entrepreneurial immigrants than in closed societies like you find back east.