I was a passenger in a car for the drive to Sun City (driven by a JNB resident who was an excellent driver). This was in 1995 so conditions might have changed, but the drive was quite nice. Road was mostly 2 lane country road with light traffic (it would be a problem with heavy traffic). Took about 3 hours driving very fast for the road conditions (doubt you as a US driver could do it in less than 4, but the road may have been rebuilt by now). Be careful about very slow trucks on the road -- you can be doing 70 mph on a blind curve and come up onto a 20 mph truck! And they will win every time. I was quite intrigued by my friends driving style until I realized he was anticipating the possible hazards; and every so often the hazards do pop up. Make sure to schedule your trip so that it is entirely in daylight, you don't want to do this drive in the dark.