Nobody can tell you if you'll be admitted or not. I've known people who got into sgu with below 2.5 gpa, so the only way to find out if you'll get in is to apply. If you're looking for a ranking of caribbean schools, everyone will give you a different answer and it's going to be biased in a way. Some people think that Ross is horrible because they have problems with administration, setting up clinicals, and the location of the school. However, I just read somewhere that Ross graduated over 500 people this year. This should be your first clue that if you work hard you'll achieve succeess in the end. I have also visited Ross and it's definately not a pleasant place to live, but you're only there for about 16 months, and if you're serious about your education the island won't affect you that much. So in my opinion, sgu>ross>auc>saba. Some other schools to consider are st.matthews, mua-nevis, and maybe aua. But, these last three schools are still fairly new and I think it will probably take a few more years to see if it will become as well established as the first four schools listed.
And you're right, your grades do suck. Your mcat score is good, and I think you should go back to school for one more year taking 20 credits/semester (science classes). If you do really well in these classes you might have a good chance to get accepted into a u.s. school. The 20 cr semesters will also prepare you very well for medical school, and improve your time management.