Ditto what Scubaman has said. I have looked into this issue for decades. As far as I know, you have a choice of taking the "product" offered from the rental car company (liability insurance) or declining it. While I have rented from many different companies in SXM over the years, I think your best bet would be Hertz, since as it was stated, Hertz includes the liability insurance in their rates, which of course tend to be higher. If you go with a non-affiliated local company, I can tell you that in the past I have rented from Unity and their liability add on coverage was reasonable.