Technically, its B-Real with Cypress Hill.
If you mean mainstream, there are Mexican rappers that had mainstream appeal, but were never on the popular level like Drake or 50 Cent.
Frost
Lighter Shade of Brown
Lil Rob
SPM
Baby Bash
All had top charting singles, and definitely got a strong fan base in the Mexican community. The rest of the US not so much.
The problem is, most Chicano rappers, don't want to expand outside of the Chicano Rap world and don't want to "sell" out even though half their albums sound like a generic mainstream album. There are only very few Chicano rappers, that are even good. Way too many garbage one's out there and this is coming from someone who grew up on this music.