It depends which countries in Africa you are planning to visit and if you will be close to a major city.
I used my credit card in most major cities, and also used my debit card to withdraw cash for when we were travelling to remote areas and the chance of finding an ATM was low.
There are a few western banks across Africa, including ANZ and Barclays. The fees for withdrawals were very high thought (averaged AU$15 per withdrawal) plus other bank charges. If you have an ANZ account and use an International ANZ ATM, you will still be charged, but at a lesser rate.
The ANZ International ATM locator is: http://www.locate.anz.com/anz/international but they do not list any African countries. I do happen to know that there is an ANZ ATM in Gabarone, Botswana because I used it. about 8 years ago