I would like to know what the $20 pp departure tax is used for. Personally I think it is a great idea if it is used to protect the environment and/or to make the island safer and more user-friendly. I think other environmentally sensitive areas should also do something like that. I know the Florida Keys well, and think that area could benefit from some kind of tourist tax to enter or leave.

It is used for the same things that the US and countless other municipaliites use their taxes for. For the most part, it is for operations, but I suspect it goes into the general fund.