No, this island is not named after a tequila cocktail in a salt-encrusted glass. You're thinking of Margaritaville, a mythical port which is not listed in CruiseMon's guide to the Caribbean (although he predicts you'll eventually find it, hidden somewhere in the Bahamas or the Florida Keys, if you drink enough rum while you're looking).

In any event, Margarita Island, or Isla de Margarita, is actually a part of Venezuela, and not exactly a backwoods part either, complete with large-scale resorts whose pools have wave machines and waterslides.