On the contrary, the city is more dangerous than the open road, much more so. You are safer in the country, where the people are still halfway decent. Trust me. And besides, SA is quite safe if the proper precautions are taken; no less unsafe than LA for instance. You can always go with a tour company or bus (i.e. Greyhound) if safety is a major concern/worry, but that is not nearly as liberating as having your own car.

I have done this drive with (almost) all my friends visiting SA. It is breathtaking, and the ultimate roadtrip. There are three ways to do the Garden Route:

1) Drive from the Cape to the Garden Route, and back again, which is what most tourists go. It is the shortest, and you probably have more time to putter around in one place as you are not having to continue on. That's probably about 600-800km, but not exactly sure.

2) Drive from the Cape to Mosselbay and Port Elizabeth (along the Garden Route). You can then shoot up to Joburg in one day of hard driving (west of Lesotho), or stop along the way in Bloemfontein (the judicial capital). This is about 1800km.

3) Drive from the Cape Town to the Garden Route, on to Port Eliizabeth, Jeffrey's Bay, East London and to Durban. Then drive northwest to the Drakensberg mountains (a world heritage site, east of Lesotho) for some hiking, and another five hours gets you in Joburg. I always do this route over a week and it is around 2100-2500km, and you see a great deal of SA.

If you want, I could give a more detailed routing.