It's not a translation issue in terms of translating to another language -- many Africans are fluent in English (some speak in natively). It's an issue of cultural translation, which is a lot subtler.
Many Africans (esp. people who can read and hence use the internet) speak English fluently. In some countries many schools teach entirely in English. There are dozens of languages in Africa, software aimed at the western market is rarely translated to African languages, hence many Africans would use Facebook in English.
That's the key. "I'm interested in men's soccer" and "I'm interested in men" are expressing two completely different meanings of the English word "interested."
I can see that happening if they've gotten sick of all the crappy en-to-* translations on the web. Even if your English isn't very good, it's probably easier to read English than a crappy translation. (Not FB in particular, just as a general habit.)