Its not very cheap to hire its sometimes cheaper to hire a driver (taxi) for the day ,but if you are travelling around the country I have a few links I can send you.
But for general info theres..
AB rent a car just outside of the Senagambia hotel.
Avis have 2 offices I think one close to Senegambia.
Halifa Salah: PDOIS is however realistic. It is fully aware that the Gambian voters are yet to reach a level of political consciousness that they rely on to vote on the basis of Principles, policies and programmes and practices.
if you hire someone make sure you can see a tax disc, police patrols costs money, also make sure you put the petrol/disel in the car. also look out for them "giving their friends a lift" not far down the road. Confirm the time, if you want if from 10 - 4 make sure you have 10-4pm your time, allo w for any ferry crossing, important VIPs crossing the roads, it can be blocked if someone arrives at the airport this is my voice of experience enjoy