We just got back from a weeks worth of partying in Negril. We've never been to RIU but I would guess they have lots of things to do at night on site. (bars, disco, etc.) There is plenty to do at night off site as well. We aren't exactly the "late night party" experts but others on here have posted plenty of stuff about Roots, Alfred's, Margaritaville, the Jungle, Scrub-a-Dub, the Rooftop, etc.
I can't say how busy these places will be in November but I'm sure you will be able to find something to do.
Have Fun!
