Apple has opened up turn by turn directions in iOS 6 for South Africa.
Apple's website stated that turn by turn directions would become available in South Africa in October. Luck for us Apple has open it right at the begining of October. Now you can get turn by turn voice assistance.
The turn by turn directions will work just like a normal GPS however the voice over is controlled by the Siri database so it might not get the pronounciation of some road names in South Africa.
You might be a bit nervous to trust the direction but be assured that Apple uses Tom Tom navigations systems for GPS so it should be reliable.
The turn by turn feature is only availbale to uses using an iPhone 4s and the soon to be released iPhone 5. If you have any other device you are out of luck.