I travel to Cape Town regularly. I've been kiting for about 8 years, so probably rate as a beginner/intermediate kiter.
I've not done anything special as far as getting on the water is concerned. Obviously things to do are:
* check the weather forecast
* go where other kiters go
* be respectful and
* enjoy yourself
Blouberg area has many beaches and parking spots. I prefer Dolphins Beach because it's close to a hotel with a bar, plus plenty of room to travel downwind
Langebaan has a nice main beach, easy parking, great vibe and restaurants close by.
Langebaan Shark bay is also very nice, there's dedicated parking close to the beach. No shops or other amenities though.
In all the cases above I've just rocked up, scoped out, rigged up and rode out.