I asked my friend from Nairobi what he thought about such a trip. He thought it was certainly possible, from a strictly physical point of view, and that, at least in the city, biking trips are commonplace and are often run by outdoor groups. He was skeptical about going alone, however. As he put it,
"I guess what makes it unsafe is the relative value of things. You're NOT going to get shot or anything, but look at it this way: a bike is worth
snatching from a rack here in Philadelphia. Now imagine what it might be worth in a country where it makes economic sense to swipe hubcaps off cars at intersections for resale to parts dealers "
He advised that before you go, absolutely talk to someone who knows the area and can tell you which places to avoid.