Don't know if this is of use to the original poster but I can thoroughly recommend Cape Town. I went earlier this year and was amazed by the variety and low cost of the escort scene. My suggestion, stay on or near Long Street, my hotel was completely girl friendly, they just called up to ask me if I was expecting a visitor and sent them up, can PM the hotel details.
If it's your thing there are street girls on and around Long Street but if you check out sextrader.co.za and pay for the monthly premium (about £10) you can get details of a lot of escorts. Compared to the UK it is phenomenally cheap £20-30 an hour for whatever you want, £100 more or less for an overnight outcall.
I would avoid the lapdance clubs, they were the most expensive option at £70-100 an hour.
I've been to Joburg many times for work but this was the first time in Cape Town, if your impressions of South Africa are formed by Joburg (driving everywhere, worried about crime, etc) forget them as central Cape Town is very safe, there are special police/security on every corner all night. I didn't feel threatened once while I was there.
I think prostitution and paying for sex is illegal but the police have better things to do than waste their time on this
Having punted in alot of Europe, Asia and the US I would say that Cape Town is probably one of the best destinations I have visited taking in account both the availability and cost of escorting and the overall atmosphere of the place.