As we drove down from Nairobi to Cape Town - I can honestly say that street food was not something one goes to Africa for.
Unlike other parts of the world (MEast, Asia, etc...) - it just wasnt happening.

In general, there was more diversity in food, and in the supermarkets, and the prices also went down as one went south.

Beer on the other hand was plentiful. As was moonshine.
By Vic Falls, it was easy to enjoy a cool Savannah Dry or some Mainstay with coke.
Tusker in Kenya, Kili in Tanzania, Windhoek in Namibia