If you're looking for a party, look elsewhere. Cozumel's already low-key nightlife shuts down by midnight, perhaps thanks to the many dive excursions leaving at the crack of dawn. The cruise-ship passengers mobbing the bars seem to drink enough for the whole island, and the rowdiest action sometimes takes place in the afternoon, when mojito-slinging revelers pull out the stops before reboarding. But if you're willing to shift the night action a few hours earlier, the excellent salsa bands playing a few bars and beach clubs will oblige. Join locals and resident expats for a few rounds on the dance floor and you'll be ready for bed at a relatively reasonable hour.
Sunday evenings from 8 to 10, locals head for the zócalo (main square) to hear mariachis and local, Caribbean-style bands.