The Gambians are renown for their friendly nature. Not just to tourists, but also to each other. The people of The Gambia are made up from many tribes who have integrated very well without the senseless conflicts that we have witnessed in East Africa and, in more recent times, in Europe. The largest group in The Gambia are the Mandinkas. Other groups include the Wolofs, the Jolas, the Fulani and the Serehulis English is the official language of The Gambia and is widely used.
Any local language is useful for getting to know people.
The author speaks a little Wolof, which is fine in the Kombos or in Banjul, but is of little help up river in say, Georgetown, or Basse, where very little Wolof is spoken. Mandinka is spoken widely, up river, along with Fulla and Serehulli. Travelling South from the Kombos towards the Casamance region, Jola would be useful, and instead of English, you would find French to be more helpful.