I spent a few weeks in Kenya in August, and I was not there as a tourist either. I felt fairly safe the entire time, though I was in a group at all times. Nairobi is probably the least safe part of Kenya for westerners, so I would be prepared to take proper precautions there, but nothing extreme--no different than what you would do to remain safe in any other country. The food is alright, I'm a vegetarian so I had a little trouble with that, but restaurants are very accomodating and even the famous "carnivore" restaurant in Nairobi had a "vegetarian" option. Drink only bottled water, even when you brush your teeth. Cell phone coverage throughout Kenya is excellent. "Kenyan time" moves slowly, so be prepared for that. Also, the roads outside of major cities and towns are pretty rough (or non-existent) so travelling by vehicle can take quite a while. The people are incredibly friendly.

Make sure to hit the Talisman, just got back from Kenya and it was the cutest restaurant in Karen, Nairobi. If you're staying in a nice hotel, they filter the water for you. Otherwise, bottled is best. They all speak english so no worries on misunderstandings. Safety was fine, outside the downtown area.