I'm based in Dakar and can recommend the Onimo Hotel. It runs around $100 a night with the usual free bus to the airport 5 mins away
ATC is good by Africa standards. It does have radar but still unable to vector ( all radials and DME )
There are a number of other Helicopter operator working out of Dakar, we share our hangar with two how support the oil platforms of the coast.
Check out the official ( French ) site for local charts and the helicopter hold points which you will need to know
AIS ASECNA
Most aircraft are parked on Golf apron for the night, there are a number of Biz jets and military aircraft parked there so security not an issue
Its cold in the mornings so bring your fleece
Cheers