DaCast has a lot of customers in South Africa and they don't experience any particular problems due to their location. This is due to the CDN connection that DaCast utilizes, which has a server presence all over the world.
You might see a bit more of a lag compared to someone based in Europe when publishing to the Amsterdam publishing point, if you are streaming with Flash, but it should be small. If you are streaming with HTML5, please use the custom IP approach.
Go to www.testmy.net and click on the green "Begin Test" button before starting to live stream to check out the available bandwidth you have for streaming. You should set your streaming bit rate to 75% or less of the reported Upload Speed and everything should be fine.