From San Ignacio town, take the highway heading west toward the mountains. The road crosses the Río Chinchipe — the river crossing is the clearest landmark that you've left the main route behind — and then begins climbing into the hills. The surface quickly turns to dirt and stays that way.
Collectivos run between San Ignacio and the valley, but only occasionally and on no fixed schedule. Ask around in San Ignacio's market area or at the informal transport stops near the river; other passengers are your best source of current information. A 4WD vehicle is strongly recommended if you have your own transport. For those without, horse hire is possible once you reach the highland section, though there are few houses along the plateau and you'll need to ask in whatever village you find first. The full journey from San Ignacio to the lower valley takes around four hours, longer after rain.