I think there are some mountains in the region, but certainly not enough to really hinder the storm. Maybe if the storm was traveling at a really slow pace, like under 10mph, it's possible that you may see some drastic drop in intensity, but i doubt that will happen. Years ago i saw a cat 4 go through Dominican Rep/Haiti: mostly mountains and rugged terrain. When the storm emerged on the other side, it took less than one advisory for it to gain it's strength again. I think it was Georges and maybe it wasn't cat 4 at that time, but i know it hit those mountains and it did lose some kick, but it regained it all when it hit the water again.