I don't go to a Caribbean school so I don't know the first hand experience, but from what I have heard:
Pros:
1- You actually get an MD (if you didn't get accepted elsewhere, MD is better than no MD I think we can all agree)
2- Some schools (i.e. Ross U) have a curriculum where you spend 18 months in the island and then go to NYC for clinicals.
3- Some schools (i.e. RU) are not research based, which means the instructors are only teaching and tutoring (yeah you actually get tutored by the teacher). I only know this from RU, because they came to talk to my school, and they pay the teachers so that they are ALWAYS available to tutor you. I think you can actually grasp the concepts better if you have a tutor available 24/7.
4- Location: well, one you are on an island, which pretty much means beach, sun, coconuts, all the good stuff. This also means there is nothing to do but study.
5- I think RU mentioned having partnerships with several hospitals that reserve a space for a RU student for their residency
6- Lower MCAT is accepted. Rolling admissions.
Cons:
1- The stigma that just because you went to the Caribbean it means that you didn't get accepted elsewhere. (IMHO I think your USMLE has more weight than the school you went to)
2- That since your school is not research based (chances are) you wont have as much opportunities to do research.
3- Well, there isn't anything to do on an island (unless you are in like Costa Rica or Puerto Rico) except school, and flying home is probably very expensive.
4- It costs the same as a US school
5- I think its easier for you to get a residency in the hospital your school is affiliated to, i.e. BU has an peds-anesthesia residency that is affiliated with Harvard too. I don't think going to BU would hurt your chances of getting in.
Just my 2c