A July MCAT means that your AMCAS application will not be considered complete until Mid August at the soonest, which is relatively late for both AMCAS (US MD programs) and AACOMAS (DO programs, I didn't mention this application service in my original response).
Basically, the timeliness of an application determines the number of interviews you receive, but this is nearly impossible to predict on an individual basis. With the time frame you have posted, if you are an average to below average applicant, you will probably feel the effects with fewer interviews.
Generally, an MD degree is pursued over a DO (though there are applicants solely interested in DO). MD students are better accepted into competitive specialties / programs, though this obstacle is becoming less and less every year (not nearly as bad as it was 15 years ago). A DO student with great grades and great board scores are usually able to compete equally with similarly qualified MD students.
I have no detailed comments on Caribbean schools, but beware, Caribbean schools are NOT accredited by the LCME, which means that if you graduate from a Caribbean medical school you will be considered an international medical graduate (regardless of whether or not you are a US citizen). I bring this up because it is often more difficult for international medical graduates to to enter a US residency program (a requirement to practice in the US), plus there are more hoops students have to jump through to be eligible for residency programs.
US applicants rarely apply straight to the Caribbean schools. It is usually the path chosen after a couple unsuccessful application cycles at US MD and DO schools. Financial assistance for Caribbean schools also works differently than for US MD and DO schools, so this will be something to look into as well.