Hi,
Head down to Rand airport...lots going on there and plenty of flight schools.
In particular Check out
Phoebus Apollo - experienced instructors (all part time but fly for the likes of Comair and DC-3/4/9's out in the bush.
Phoebus Apollo
I don't know if you want to do the full validation of your license (to fly solo) but this would be the best place. They're located the far end of the airport...abit of a walk, but plenty to see on the way!!
Then you've got Rand Flight Academy, Omni Flight School who I'd also recommend if your just after a few flights with an instructor. Availibility was fairly good all round, but obviously give them a call first if you want to fly immediately...especially Prometheus as instructors there are part time.
But yeah, just ask around...many many students who have been there long term - listen to what they've gotta say.
Theres also Grand Central airport which I think is nearer Pretoria...was there only very briefly but there is a flight school there. Smaller and quieter than Rand...but without doubt so much more to do at Rand (good busy cafe, museum, endless hangers with huge variety of a/c where you can just wonder in )
Very friendly airport too...have fun!!!