I would highly recommend that you consider hiring a guide for your initial outing at least. The information you can learn from doing so will help your success rate exponentially even if you decide to go it alone after that.
Though I've never been to or fished in Cuba myself, I would also recommend that you plan to bring everything with you in the way of flies and gear that will need to fish once you arrive. Like most things in Cuba, I suspect it might be difficult to locate much in the way of fly gear.
Have fun, and let us know how you make out!