OK...so I'm a few years too late...but I hope someone finds this useful...

I would second the Moyo Melrose Arch recommendation since you are in the Sandton region .
Check out the website:- http://www.moyo.co.za/restaurant-moyo...
Advisable to book, also look at the What's On tab

'Fraid not, don't know Cape Town at all.

At the Rosebank Market on Sunday try the chicken pies from the vendor next to the cheese people in the corner. They are delicious gut-fillers (in the best sense), I think they come from a place called 'The Home of the Chicken Pie' that is on the R512 heading NW out of Johannesburg to Hartbeespoort (the road that also takes you to Lanseria Airport).

For Thai/Vietnamese try Cranks in Rosebank (a funky place) and also for Thai try Wangthai on Mandela Square in Sandton. I haven't been to either in a while but have not heard anything to suggest that they aren't still good. Hope you can try them.

Have a look at eSpring - http://www.espring.com/English/home.aspx

Great to see the recommendation of Fournos' croissants, they are the best! Heaven to me is sitting at Fournos in Dunkeld on a Saturday morning and enjoying cofee and a croissant!
http://www.fournos.co.za/content/inde...

(BTW I live in Jhb)