Margarita island has been a popular destination spot for Venezuelans for many years.

I think you have to consider whom your primary (rental) market would be which in addition to locals, would be the US more than European. Americans have little interest in going near anything in Venezuela, and Vieques you can forget about. It has gotten a lot of very bad press in the US because of the previous US military base there. It was a testing ground for US bombs/missiles and many claim the island has high cancer rates.