Here's a show at my station KPSU you should check out:
http://kpsu.org/program/sudamerican_rockers
You can download shows and play streams of old ones too. He plays a lot of stuff, some is great, some is like crappy Spanish versions of famous English language bands. Overall a great resource though.
My favorite My Space find is
Santa Sangre though they mostly don't have vocals in any language:
We are LA's first and only Mexicano Nosie doom band.
We like to smoke alot of weed ,drink cheap beer ,Watch massive amounts of movies and we will destroy you !!! We call Mexican food just food....