The official languages of Haiti are French and Haitian Creole (Kreyòl Ayisien), a Creole language based on French, with 92% of its vocabulary derived from French and the rest mainly from African languages. Haitian Creole is the mother tongue of the masses, while French is the administrative language, although only 15% of Haitians can speak it and only about 2% speak it well.
Creole is mutually intelligible with French at the most basic level, so the competent French speaker should be able to cope in limited circumstances. Many Haitians are very grateful if you make the effort to learn a little of one of the official languages (preferably Creole) rather than using an interpreter or expecting them to speak English. Haitians working in tourist areas generally speak English well enough to hold a conversation.