Welcome tigersfan. Always lots to do round Negril. The beach area has lots of bars to hang at and there is local music several nights a week. The Jungle is a dance club that many go to - party starts late. Up past downtown is West End and there are lots of cool places to hang out also. Since you are new you might try some of the webcasts put on by RealNegril.com as its a cool place to meet people and have fun - on Sat night they have a live show at Seastar on Westend with live bands, etc. It is not high season but there is always fun to had. Be safe but enjoy your trip. We are alwasy happy to help so feel free to ask anything.
Cheers!