Regardless of where you buy, do your homework ahead of time and know what approximate costs should be for what your are looking for. If you buy on the island, I would only do so from a store that has a relationship with a US based repair facility. I personally know Caribbean Gems and Ora Diamante do as they are sister stores and we have purchased from them and when needed had repairs done through their US based affiliates. I am sure there are other store that have the same arrangement and that is something I would want.

You will for sure save on tax and often jewelry is a much better deal on the island but I would do come comparison shopping at home also.