Vietnamese would be easier to recognize/do a translation pack for too, now you mention it - basically the Latin alphabet with extra marks to make 30 letters. Apparently there are more north Vietnamese around here and Oakland, more South Vietnamese in SJ and down south, maybe 450k in all of CA. Chinese-American maybe 5-600k? More than 150k in SF.

Incidentally, there's other and easier untapped startup opportunities for the Asian language demographic, if anyone wants to send me a note via gmail

My in-laws are a mix so either language is good, both is better. I can promise 3 Android and 1 iPhone sale just in my home :)