Juanita, it depends on your audience. Are they Mexican, Mexican American, Hispanic (assorted), or all gringos? I'll be playing at an Irish Pub but I may throw in "Cancion Mixteca" since it is 5 de mayo. If your audience is all gringo, how about something like "Cielito Lindo". It's about as overdone as "Danny Boy" on the Irish circuit but everybody will recognize it. By the way I don't mean "gringo" to be perjorative, just want to distinguish between Latins and "middle Americans" - in terms of whether or not they would understand Spanish lyrics or be familiar with some of the better known Mexican songs.