This question of skipping JNB comes up over & over in this forum. As you'll see when you read the previous posts, you can not understand modern political South Africa (or its obvious implications for U.S. history and culture) without visiting Johannesburg & Pretoria. So, that means you should skip JNB if you're not interested in that. And conversely, you must go to JNB if you are. The previous suggestions about the Apartheid Museum, Soweto and the Hector Pieterson Museum, the Voortrekker Monument, the CBD, the northern 'burbs, etc. are correct.

David