Charter boats take travelers from Guanay to Rurrenabaque, but these are pricey to arrange on your own (B$4000 for a 10-person boat, 12 hours). Several agencies in La Paz offer a multi-day version of this trip with camping and jungle excursions from about B$1990 per person. These include Deep Rainforest, Gravity and Banjo Tours.
The bus offices are all located around the plaza, but buses actually depart a block away toward the river. Four companies offer daily runs to and from La Paz via Caranavi and Yolosa (B$45, 10 hours). Departures in La Paz are from along Av Las Americas daily at 1pm or 1:30pm (10:30am on Sunday). For Coroico, get off at Yolosa and catch a lift up the hill.