I am relatively new to windsurfing having taken the sport up 1 year ago.
I briefly considered kiting, which is I believe is the most serious threat to the growth of windsurfing, but having sailed yachts in the past, the similarities brought me to windsurfing.
Recently I introduced a young yachtsman to windsurfing and he was instantly captured by the experience.
My point is, that the sailing community (I can only speak from experience in Australia) is, I believe, a fertile field for promoting windsurfing. Sailors understand the wind, appreciate the mechanics and hardware associated with the sport, and find rigging / de-rigging a minor inconvenience compared to yachts. The speed and thrills, of course are incomparable in any other sailing craft (IMHO).
I can imagine information / trial sessions at yacht clubs instantly being successful. In addition, the clubs themselves may find it an excellent marketing tool to attract a new class of member.