I have a friend from Cali who's half Mexican, in jail he was a Mexican and on the streets he is a Mexican. Most people find the dominant gene and run with it.
That is more a race sense though is it not? That is the thing Cain isn't representing hispanics he is representing a specific Hispanic country that he has no direct personal link to. He isn't carrying around a symbol of hispanic pride he is carrying around a flag of a specific country.