If you haven't taken MCAT, then you most likely haven't applied to Canadian med schools as I'm pretty sure all require MCAT. You should go through at least 2 to 3 cycles of applying to Canadian med schools before considering Caribbean schools. You should also not consider Caribbean schools before attempting MCAT since its an inexpensive way to get an idea whether you are likely to be successful at a Caribbean (or any) med school. A 500 on the MCAT likely won't get you into a Canadian med school but would at least give you an indication that you are competitive for a Caribbean med school and might have some chance of success.
Most top Caribbean med schools have around a 30% attrition rate, so even an average MCAT is no guarantee of success, and Caribbean med schools are a lot more expensive than Canadian med schools which are heavily subsidized by the government. Failure will leave you (or your family) thousands of (US) dollars in debt. Provincial student loans will only cover about $12,000 a year, which isn't even one semester's tuition, and few Canadian banks will make unsecured loans to Caribbean or other international schools (no matter what their web sites may say). SGU is probably the most expensive of the Caribbean schools, but probably the one with the best likelihood of success. I wouldn't even consider any other than the "big three" of SGU, AUC, and Ross.
Finally, even if you are successful, if you want to practice and live in Canada, Caribbean grads are considered International Medical Graduates in the Canadian Residency match and are streamed to a limited number of specialties, mostly family medicine. You've got about a 20% chance of matching to a residency in Canada and a lot less than that to a specialty other than FM. Most Canadians who go Caribbean tend to match to residencies in the US and try to find a way to stay in the US, but there are Visa and immigration issues that can make that a challenge. Some are able to make their way back to Canada eventually after residency, but its tough and expensive doing Canadian exams and getting licensed all over again in Canada.
Bottom line, do the MCAT and try and get into a Canadian med school before even considering SGU or any other Caribbean (or international) med school.