Good on ya Fez for trying to make your local safer and inform all water uses, not just one type.
Your best bet would be to have a friendly chat to the other local windsurfers and kiter on the beach, some may not realise there is even a problem, unfortunately.
That way you are getting to the root of the problem and not wasting your breath on posting here where they probly dont read, and where the usual couple of negative haters will immediately try and troll it into a "I hate kites" thread. And not actually give you any advise or help the problem.
Try the "have a friendly chat" on the beach thing, you may be surprised how most will cooperate making the session more enjoyable for all and your stress level lower, all from a quick chat.
Remember, a stranger is just a friend you havent met. lol