It's quite a few years since I was there, but I'm afraid there was little evidence of windsurfing then and all the reports I've read since have suggested the windsurfing scene is fairly pants (a few plastic planks at the hotels sort of thing).
Brian Talma did a bit of a write-up (in his unique _style_y)
http://www.irieman-talma.com/stories/cuba.htmlThere've been a few threads on the Boards forum too, normally descending into a me vs the lefties spat, but there is some useful info there.
It's a fabulous country to visit though. There's the wierd time warp thing, mixed with the Latin/Caribbean culture, mixed with one of the last bastions of nutcase socialism, mixed with lovely (if poor and oppressed) people.
Do you plan to travel around on your own a bit? That would be my top tip. Me + ex rented a car and it meant we could get off the normal tourist trail and out of the bits you're expected to stay in. We (unlike the locals) had no hassle from the police / state services and I suspect tourists can still (or even more so) do as they please as long as they keep bringing dollars. The only scary moment was when we were flagged down by two soldiers, but it pretty soon turned out they were bunking off work, wanted lift home and had worked out they could pass through police check points without stopping if they were in a tourist car. They dived onto the floor when we approached a check-point.
So, don't expect to get a decent sail, but you will have a brilliant time.
Oh and the rum is fantastically good.