I got to talk to admissions officers from several Carribbean schools lately (and also got information from pre-health advisors on the subject), and for what it's worth:
Apply to Carribbean schools only as a last resort. With that said, Ross and St. George's are among the most respectable of the Carribbean schools. There are some reasons why some people will succeed at a Carribbean school, namely they have the drive and passion to succeed in becoming a physician, even if it means living in another country for a couple of years to pursue it. Conditions (living and medical-school related) may be very different from what you are used to in the states. But, on the other hand, you will be exposed to much diversity, in terms of your classmates, your patients, and possibly the diseases you will encounter. You will get about the same education as every other medical student in the U.S., and you will do rotations along side other U.S. medical students. In talking to admissions officers, every school I talked to gave me their 2002 residency match list. Every student matched to a residency in the states, with the exception of a student I noticed who got a residency in England (I don't know, maybe he was from England?). I saw just about every specialty represented. I don't know how great these programs are ranked (the quality), but everyone who wanted a residency in the states got one, from what I understand.
In the end, will your patients really care where you went to med school? All that matters is that you come out a compassionate, caring, and competent physician, whatever the route. If you think Carribbean schools are the way to go, then don't let anyone stand in your way.
On another note. Have you been tested for learning disabilities and/or physical impairments that could be hindering your performance on the MCAT? Look into it as soon as you can, unless you've already done so.
Good luck.