I have a new fourth-favorite Austin radio station for those times when I'm in the car and there's nothing good on KUT, KOOP or KVRX. It's KXXS 104.9 FM "El Gato" where you can hear a little banda and a little tejano, but mostly you'll hear cumbia cumbia cumbia!
It's not your hip intellectual college-kid cumbia, it's strictly Mexican top-10 cumbia, but that's okay. You can match your Spanish against puzzles like "La cumbia japonesa" in which l is substituted for r (¡Mueve la cintula!) and if you don't understand the lyrics the first time, don't worry, they'll rotate back around within the hour.
You'll know when you've found it because of the tomcat howl after every song. But don't look for a website -- El Gato don't need no stinkin' website. ¡Búscatela!