There are a couple...
is sort of the unofficial SA kiteboarding page.
Alternatively check out http://www.capesport.co.za/
which gives details on accommodation, kit rental if required etc.
If you wanna check out the spot, there is a 5 minute section in Powerzone 2 on Cape Town.
To give you an idea of costs, a beer will cost you around $0.60 in a pub and around $8 per 24 in the liquor store. Big Mac combo is around $2. If you go out to a 5 star restuarant for a very good quality steak expect to pay around $5 or maybe $10 if you include starters and wine. (Cape Town is the centre of the SA wine industry, make sure oyu tour the wine farms which produce some of the top wines in the world)
That should give you the basics of what you need to know. Enjoy