I have been to many costume parties and have seen many people dressed as either Speedy Gonzalez or the Frito Bandito. Usually they are white people trying to appear Mexican, but they very seldom pull it off.
That changed, however, last year when a Bernie Jensen, an actuary, and Jim Derdoski, the local pharmacist, showed up at the party dressed as the aforementioned characters.
Everyone at the party was shocked at the incredibly convincing manner in which they had transformed themselves into the likeness of Mexicans....
So, it can work.