I'm from SA, but staying in Finland now.
Internet in SA is slowly getting better, but a lot of the people I know there don't stay logged in due to having data caps. Just log in for specific stuff and maybe browsing for an hour or two.
The physical connections are all served by a single, government-affiliated company which drastically overcharges for line rental and data costs which is why the service providers have to have data caps. And mobile data isn't cheap either.
Anyhow, good luck with the trip and have fun! Enjoy Cape Town if you do manage to get down there, it's a great place.