In this category, I think Manuel Ortiz and Oscar are the top 2. After that, its close. You got guys like Tapia, Rodolfo Gonzalez (I think he was Mexican American), Canizales, Carbajal, Danny Lopez, Chacon, Mando Ramos, Palomino, who could all make the top 5.
Would Chalky Wright count? He's from Arizona by birth, but was believed to be Mexican by most at the time. If so, he's definitely third IMO.
#05. Michael Carbajal #04. Johnny Tapia #03. Chalky Wright #02. Oscar De La Hoya #01. Manuel Ortiz These are my top five, without too much thought. There's no way that's accurate though, there has to be some US greats with Mexican heritage.
I think Chacon was a better talent than Carbajal - but it sure helped that Carbajal had one punch fight ending power in either hand.
What about Mr. Opposite. Born in the USA but moved to Mexico as a kid and lived his whole life there.