Lanseria best place for sure. Check the requirements though. It's quite a while since I last flew in SA, but they did require you to get a SA PPL - assuming you are a foreign PPL holder. I had to do an air law exam at the SA CAA HQ in Pretoria and a flight test. Also consider that as Jo'berg is 5000ft up, you may want something more powerful than a C172, especially if travelling out to the Kruger.