Between there and Sandton City / Mandela Square should be fine. Personally I wouldn't venture much further than that although I may be erring on the side of overcaution.
It's actually an ongoing question in my mind how safe the Sandton CBD is on foot after a certain time of day. The thing is, other than the malls and hotels, central Sandton consists of business premises: about 100,000 of us come in to the area every morning and vacate it again at the end of the day. Which means it's a lot quieter without us. I've made a personal choice not to leave the office (and do my 1-kilometre walk to the Gautrain station) after dark, but as said,perhaps I'm being too cautious. There are always private security guards around - that does have to be said.Edited: 14 January 2016, 05:27
Just to clarify after reading this over: I wouldn't hesitate to drive in central Sandton - and have done so countless times - at any time. My reservations are purely around walking in the area.