All of the lead characters are not white. Jamie Lee Curtis is white and portrays the stereotype white, Beverly Hills lady who throws obscene amounts of money around and shows it off everywhere she goes. Piper Perabo is her somewhat self-centered niece. Only two white main characters.
George Lopez is one of the main voices. Most of the movie takes place in Mexico. “Hello, they are chihuahuas mijo”.
Why wouldn’t Latinos voice these characters? It is a cute movie geared toward children who don’t think twice about the people, characters, voices, dialog, or settings. They see talking dogs who are in Mexico and who have a different accent than many of them. They find this interesting if they think about it at all. Your phony boo-hooing is what will seep into their little minds eventually and skew their open-minded outlook on life.
I doubt that all of the Latino actors who wanted to be involved in this movie are in need of jobs. Have you seen the list? Just watch the movie before you judge it unless, of course, you’re afraid that if you do you won’t have anything to gripe about. Watch it with a young child if possible and try to see it through his or her eyes. That way at least your eyes will be open.

ps
try watching the CURRENT trailer not this old one that they don’t use.