Probably because alot of the Mexicans in So Cal, especially in the San Diego area have been there for generations and have more White blood in them. But the ones you're seeing in the south east are beaners who probably still have wetbacks from swimming the river. Most of the illegals coming here are more indian types, whereas alot of those southern CA chicanos who have been here for generations tend to have much more White DNA. Some of them are even descended in part from families of White(Spanish) Mexicans who have lived in that region since before the Mexican American war.