Come home. Nothing against SGU specifically, because it's one of the few well-regarded Caribbean schools out there. But when it comes to getting into an American residency program, having a Caribbean degree would already be a huge disadvantage even if you were applying for residency this year. As someone who would be graduating four years from now, you'd be facing even more difficulty with being squeezed out of the residency running by a glut of American grads. It's going to keep getting worse for IMGs every year as American schools (both MD and DO) keep expanding their classes and new med schools keep on opening. As an example, eight years ago when I applied, we had four MD schools and one DO school in my home state (FL). Now there are twice as many FL schools of each type. That's a national trend.
Concerning the issue of applying as an ex-matriculant, I'm going to respectfully disagree with Goro about how serious of an issue it's going to be. I do think you'll have to do some explaining, and you're going to need to take the next 1-2 years to get your ducks in a row before you apply again. But speaking as someone who spent four years as a student adcom, I wouldn't hold it against you for a second if you got cold feet about attending a Caribbean school. In fact, I try to talk everyone who asks my opinion out of attending Caribbean schools, even one of the Big Four. First, it's expensive. Second, a lot of Caribbean students never even make it to the point of applying to residency; those schools have very high attrition. Third, of the ones who do make it to the residency app point, a significant number either end up in a specialty they didn't want or don't get a residency slot at all. Again, that is a problem that is only going to keep getting worse as US schools put out more grads and more IMGs get shut out.
I also think that your point about having family close by for support is valid and realistic. In fact, it shows insight and maturity to have thought about these things. It also shows courage that you are willing to admit when you have made a mistake, take a step back, and put your effort in a more positive direction. Continuing down a path that you know is wrong just because you don't want to look like a "quitter" would be a bigger sign of poor judgment to me than not starting classes at SGU.
Finally, while some med schools might hold a mistake you made as a 21-year-old (assuming you're a trad) against you, others won't. I made some stupid career decisions when I was in my early 20s too. That's why I wound up going to med school at age 31. There are an awful lot of other nontrads out there who screwed up in their college years and are making good now. Fortunately for those of us who didn't have it all together as college kids, our med schools were willing to give us a second chance.
Just thought you should have a different viewpoint, because I agree with you that staying at SGU would be a mistake for so many reasons. Hope this helps, and best of luck.