Afrikaans and Xhosa are the most relevant local languages to Capetown.
Afrikaans is not huge, but fairly active.
Xhosa has a tiny number of contributors, but they are dedicated, and I think that at least one will be at the Wikimania.
Other languages of South Africa in which there is a Wikipedia
There are many other languages in South Africa, and there is a Wikipedia in most of them, although activity is unfortunately very low even though they are spoken by quite a lot of people. See: