Cheetah
I did most of my flight training at the Tree and I have never encountered anybody that was not able to converse in English. Worst case was the airport cleaner, but even he mastered at least a Level 4. Your references to the boerewors curtain and the hideous, primitive African dialect, are a little ridiculous. You can do better than that, I'm sure.
I think the problem is rather discipline. The students are not given the time or the necessary radio training before being let loose into the circuit or the GF. And here it doesnt matter what language the student speaks at home.....even the educated ones have trouble talking to ATC.