BTTB-
Let me just say this...
I was sort of in your shoes (sorta) when I started Ross. Except, I'd been out of school for a long time and I had a somewhat older than usually accepted MCAT score (albeit a strong one). I believe that I probably would have been shoved into that "first steps" program had it existed at the time. However, it was initiated after I matriculated.
Let's just say that I made it off the island in sixteen months. My overall GPA was high enough that I didn't even have to take the comprehensive shelf. A substantial number of people in my class, ones who'd come straight out of college with Biology or other science degrees, did not. Many of them are still down there sitting in the BMSI.
I do not believe that this course is necessary for you to get a good GPA at Ross. I was a non-science major in undergrad (years ago) receiving a B.A. Much like yourself, I took essentially the "bare minimum" pre-med courses. It all comes down to how hard you want to work. My motivation was having to stay in Dominica an extra four months.
I'd do some soul-searching if I was you, and really consider whether or not you think this class will be helpful. Based on what I saw and experienced, I don't think it is. However, this is only the second semester that they've had it running. So, it's bound to get better with time, and maybe when you get there. Start in May, though, if you go do it.
Another option: start at AUC or some other Carib school and transfer to Ross after a year or so. They accept in-bound transfers (if you've done well at the other school). Remember, they want your $$$. (Not an indictment, just the truth.)
Or, you could always hold-out and say that you're not going unless they offer you full matriculation straight into the M.D. program. Stand your ground. They're likely to cave, and even if they don't they won't rescind their offer for the "first steps".
Good luck, buddy. Exercise other options if all else fails (and, if you have them).
-Skip