If you're on the north coast over the weekend 26th/27th/28th November the annual Cabarete Jazz Festival will be on. I was coincidentally in Cabarete a couple of years ago when this was on. Even as someone who isn't a huge jazz fan, I had a great weekend. Cabarete was really busy, especially on the Sunday when lots of Dominicans visited the beach. There was a large stage built on the beach and a great atmosphere. If you can be there, make the effort.
A few photos from 2008: