I think right now I'm going to label Puerto Libre as a United States Associated State, kinda like Palau, but with more... liberty. They've got their own currency, system of government, infrastructure, etc. but they also have a US embassy, military base, and an agreement with the US that allows Puerto Librens to live in the US as expats and vice versa. They're sovereign and autonomous in all matters but military, and even that's negligible-- the biggest US influences on Puerto Libre are language (most people besides the Natives and Tribals speak English, or some understandable corruption of it) and business.

And yes, they're a HUGE tourist trap-- both for people looking for the paranormal as well as normal vacationers that want the Caribbean experience without as much of the sun.