Be as objective as possible in your decision. And, I agree 100% with everything that Pioneer Research has said. DO or MD, wherever you get them, will mean nothing until you prove yourself on the wards. Becoming a doctor is a long, LONG process that doesn't start or end with a particular school you went to or where you did your residency. You have to be committed to lifelong learning.
Now, many SGU and Ross (and I'm sure a lot of AUC) grads do indeed get competitive residencies. Check their websites. Nonetheless, I think it was expertly pointed out that the top choices are even tough to get among U.S. grads. Some schools will, however, flat out refuse to even entertain applications from IMGs. Is that right or wrong? Who knows. But, it's a fact. Likewise, if you have dreams of orthopedics, dermatology, ENT, or some other very top residencies, you might want to wait it out and reapply to a U.S. school. It will be very hard if not impossible to get one of those spots coming from the Caribbean. About 70% of Ross grads go either Internal Medicine or FP. I think the same is true, more or less, for the other Carib schools.
Lastly, before you decide to go ANYWHERE outside the U.S. as a U.S. citizen, you should read every single word on this website:
http://www.aaimg.com/
This will help to put a lot of perspective on your decision and choice about where to go. (N.B.: I know that they need to update their information on St. Matthews, which has relocated to Grand Cayman and has gotten a lot of their deficiencies straightened out. I have sent them an e-mail regarding this.)
Good luck whatever you choose.
-Skip Intro
MS2 Ross University
Portsmouth, Dominica
P.S. Currently, in our third semester class now on the island, there are 4-5 SGU students who transferred here. From what I understand, they did so because they did not want the chance of having to go to England to do some of their clinicals. Not saying that's good or bad or anything else; it's just meant to be information.