Argh, I know how you feel. I haven't been to Africa yet but I've lived in the jungles in South America and South-East Asia, usually living in villages; food is a huge
issue! I always make sure I have some protein bars with me, and although I don't take supplements at home, I take them when I'm travelling. If you've got sufficient supplements, hey, you can be happy on purely fruit and vegetables for a while. Learn a little bit of the language - enough to say that anything containing meat, meat stock, dairy, eggs, or any animal product will make you violently ill
And always know how to say "plain vegetables with rice". Not too exciting but it'll get you by when you're eating at restaurants with primarily meat-based menus.
Having said that, do try and get to some local vego restaurants to sample some fabulously awesome vegan Kenyan dishes!