The bus leaves from San Isidro at 5:00 a.m and 2:00 p.m and take two hours to get to San Gerardo de Rivas. Returning at 7:00 a.m and 2:00 p.m.
Head to the south of San Isidro via the Interamericana, and cross the Rio San Isidro to the extreme south of the city. Some 500 meters away you will need to cross the Rio Jilguero and look for a road on the left, 300 meters away. A small wooden sign with yellow letters will show you were you need to turn off. There is also a red sign that says Universidad Nacional. If you come from the south, there are two entrances to this road, easier to identify with the red signpost. The forest post is some 18 km along the same road and is asphalt up until Rivas, after Rivas it is a transitable gravel road.