I never been to that part of Africa (only Madagascar & Morocco, so this is maybe pointless), but I've been to loads of other places as a vegetarian. It's generally not a problem... apart from you have to communicate you don't eat meat, or eggs, or whatever. That part can be difficult. But everywhere has rice, veg, and pulses. I wouldn't worry about offending people either. People might think you're strange, but won't be offended. I reckon you'll get toasted on roaming fees, though.