The above suggestions are all correct and I agree %100..
However, if you want to just store and IF your insurance
will allow it, there are yards in the northern islands that are MUCH MUCH cheaper than either Grenada or Trinidad. They use all the same proceedures and secure your boat in the same manner, they are just further north. It seems the prices in both Grenada and Trinidad have climbed over the last few years and all the yards I priced in both were about the same.
As a point of reference, we were looking at about $750-800USD/month to store our 40ft Catamaran
in either place. More northern locations are about 1/2 that cost.