You get planing in a Force 3 and by and large kites require less wind than windsurfers.
You can take part in this sport, like windsurfing, anywhere there's water - but beware. Learners need lots of room because those lines can be like cheesewire in the wrong hands. A good launching and landing platform is very useful because someone has to help you land the kite on dry land. Oh and don't even think about going out in an offshore wind.
Flying the kite is around 80% of the learning curve. Just because you've ridden boards before doesn't prepare you for handling a kite or learning about the wind.
You're best off buying a mag on the sport (which country are you from) and going from there.
Regards
Matthew Farrah
www.totalfootball.com Bath, UK