If you have never driven here before, there is a good chance you will get hopelessly lost (sorry if this offends anyone, but Dominicans don't know how to give directions) or you will end up in a bad accident on the mountain highway. The signage is usually awful or non-existent, the drivers suicidal, the horses jumpy, the potholes deep, and land/rock slides extensive, and the moto conchos vengeful. Its good to know what to look for on these roads, and you only get that with expperience.
Once you're in Cabarete, its fine to have a rental, I am just talking about the road from Santiago.