Senor Fish in Little Tokyo used to have rock en espanol night on the 2nd Saturday of each month. They would have a live band in front and pop en espanol with a dance floor in the back, made for a great mix of people. They would also have a lonchera parked in the back for all your taco needs <3
Senor Fish, they don't seem to be updating the calendar as well as they used to, but keep a look out, all the bands I've seen play here have been decent at the very least.
I think the best way to keep in the know about this kind of stuff is to check in the LA Weekly... and if you hear of anything good, let me know