They rarely circulate after 2030. They are difficult to manage with luggage. For example to get directions to the departure point for buses to Cap-Ha tien, ask for the station Au Cap. Most of the stations are somewhere on or between Boulevard Jean-Jacques Dessalines and the waterfront. There are no fixed departure times.
Buses leave when they are packed.
Roads are bad and journeys are long and uncomfortable. In trucks, it is worth paying more to sit up front with the driver. In Jacmel buses leave from the gas station at the junction of Portail L ogane and Avenue de La Libert . Go up Rue 22 for about 10 mins walk, ask if you get confused, it looks a bit rural. Taptaps will drop you at the gate to Coco Beach.