Sacbé is just far enough outside of the touristy downtown core to attract locals. The crowd at this trendy tri-level club is usually really young (it's a bit more mixed when hosting the odd live-music performance), but there are plenty of couches to lounge on if you're too intimidated to hit the dance floor. The music is a mix of the latest international and Mexican dance and pop hits. The cover is totally reasonable (never more than $5).
Calle Ejido at Guerrero, Zihuatanejo, 40880, Mexico