You would be wise to only use cash in Cameroon - the Central African Franc (FCFA) is the only form of payment in much of the country. Credit cards are accepted in some establishments, but fraud is endemic. Counterfeit currency is a growing problem.
Like most countries in West Africa, Cameroon's road networks, both paved and unpaved, are poorly maintained, poorly lit and unsafe at all times of the year. During the rainy season, many roads are barely passable even with four-wheel-drive vehicles.