The train is an excellent experience, reminiscent of the colonial days. There are also trains to Kisumu, Malaba, Nanyuki, Eldoret, Voi, Taveta, Kitale. If you can stand the pace and the avant garde driving style, buses are frequent and cheap, connecting all parts of the country using Nairobi as a hub. Cheap and colourful servicing many city destinations as well as outlying routes.
TAXI Taxis are quite cheap and plentiful in Nairobi, Mombasa and other cities.
Many are decrepit but there are also dozens of London 'black cab' taxis operating. Always agree the fare before starting the journey. On the left hand side of the road as in Australia, Japan, UK etc. Some roads are in poor condition. You can drive yourself or take a driver with you for a little extra cost.