Have a look on http://maps.google.co.za what the length of the route from your house to your exchange is - the telkom cables probably follow that route, or something like it. If it's under 3km, you have a pretty good chance of having a reasonable signal. Under 2km and your chances are better.
Check with your neighbours (make some new friends) what kind of ADSL speed and quality they have. If they all complain about their ISP's, then you're going to complain too.
Lately telkom seems to think that 4Mbps is some kind of baseline that everything probably does support - they're trying to keep up with the rest of the world, which is nice.
Also, Telkom stubbornly refuses to offer ADSL on pay-as-you-go, so your first problem is converting to contract. (Please correct me if they have quietly changed their stubborn corporate mind...)