The company line: Kitesurfing can be dangerous to yourself and more importantly others around you. While we might not be too bothered to lose you as a valued customer, we'd be quite upset if you took out a beach load of valued customers.
if you know boardsports and have flown a variety of big kites, and more importantly have been dragged up the beach at 100 miles an hour and lightly injured yourself a few times, then you know what you are in for.
As a minimum take lessons to cover the basics of safety, set-up and emergency pack down. You don't need anyone to teach you how to kitesurf, actually get up on the board and go, turn, and jump, all that jazz.
But you do need someone more experienced to teach you safe methodologies for attaching lines and bar, weigthing down your kite prior to launch and how to and when to safely activate your QR and safety systems.
You need someone to tell you where to ride and where not to ride. To tell you what conditions are safe and which aren't.
Getting on and off the board is the easy bit, it's all the other stuff you need to learn.
If you were a snowboarding, windsurfing, paragliding, sea kayaker with power kite experience, then i'd say go for it, but otherwise its worth investing in a few hours of one-one. Don't do group lessons.