Hi, I can only tell you about spots near Cape Town. They're brilliant!
Firstly a good resource to check out would be:
http://www.kitespotters.co.za/kitespots_wc_map.phpI can tell you that the whole Blouberg, Tableview area is a nice spot for kitesurfing in Cape Town. Dolphin Beach, Big Bay or Doodles are the main spots I think.
Otherwise check out Langebaan about 1h drive from Cape Town for the smooth water lagoon. Some people make the mistake of kiting at the front end of the lagoon which is also OK but there's a much better spot at the end of the lagoon. Just ask around in CT or if you're staying somewhere in Blouberg, ask the local kiteshops where excactly it is.
Try going to Witsands (not to be mistaken with Witsand, which is further away). Very nice spot. Oh and don't forget your wetsuit, even in Summer the water can be really cold. Oh and another thing, don't fall, you'll like a huge lure for the little sharks......just kidding, just kidding.....they're aren't actually that small
I can't say anything about the rest of the country as I haven't visited them yet. I've always stuck to Johannesburg and Cape Town, but when in Durban, try contacting a guy called Rob Chrystal (he's a local f-one dealer) landline +27-31 562 8886 or cellphone +27-82 88 01 888. He'll help you out with Durban or maybe even take you along for a session or two.
Partying: well I guess there are lots of places to party, you'll probably get invited by some locals for a braai (BBQ) share some beers etc.
For real clubbing and going out, you'll be best off in the center of Cape Town (Long Street and also Loop Street are probably the best places to hang out.
Do's: Be friendly, respect the local rules of the spots, especially since there are a lot of waves around and you have many waveriders around, you'll be best off to respect their 'territory' and learn the right of way on the water and waves.
Be social, talk to the locals on the beach. Most are really friendly and open and you'll be invited for partying or get great local tips.
Don'ts: don't land up in jail! whatever you do, just don't. The next morning you'll have a nigerian drug lord quality assured stamp on you ass. If you ever get stopped by the cops and it gets down to business and its so messed up that they want to lock you up, start bribing
otherwise always be friendly and everything should be alright in good old Cape Town.
That should be it. SA and especially CT are really nice. You'll enjoy it.
http://www.tablemountainview.com/ it looks a bit misty right now, but watch the cam when the sun is out. Its beautiful. Enjoy Cheers