I was not going to post but I really like to mention a few things considering that I live on the caribbean (Puerto Rico). First I have been on 6 cruises so far and I have always book my tours directly from the company.
Because you are safer that way, not all the islands are safe enough to venture yourself alone or to be wiser than the company ($$$)...
I have a friend in the st Thomas border patrol and he told me that every week some cruisers are left behind the island by a cruise company becuause they don't arrive a the time the cruise line ship leaves port,
St Thomas is a small Island if you think you can rent a car, travel around the island without problems think again, remember they don't have interstates, so if you are in the other side of the island it will take more than 2 hours arrive to the port if there is a car jam and many cruisers think "two hour is enough to get back" and forget that around 3 pm everyone in the island is off work getting to their houses.
also how much chepear that is 25 dollars?? 50 dollars??
try to think
if you are left behind how chepear this will be or if they hit you and take away your passport and money...
also, living in an island, I know for sure that you have to be careful where you go
not all the people of the island are friendly and if you don't know where is the crime how can you avoid it?
so In the end, for me, is not an option
When I go in cruise I like to leave my problems at home not to get new ones
but that is just me many cruisers do it the other way and never had a problem...