When I was cabin crew, we heard all kinds of horror stories about pretty much all our African lay-overs. Most crew refused to leave the hotel in most of them, which was a shame, because there was masses to see and do, and I never felt remotely threatened when out and about. I just wore grotty old clothes and looked like I knew where I was going.
Lagos was the exception. I went out once, and only once. Not only because of the threatening atmosphere and being constantly jostled and hassled, but because the place is chaotic. I'm anything but a scare-monger, but I'd say: Be very careful if you go there, w-c.