Tracopa operates the buses that run between San Jose and Uvita. They leave hourly from 6 am to 3 pm.
You can take all buses with destination Ciudad Neily, Cortes, Paso Canos, or Golfito. All these buses drive down the coast (“x costanera”). They will all stop in Uvita. You recognize the stop in Uvita by the bus terminal with takeaway restaurant, Flor de Sabana.
The walk to Hostel Cascada Verde is about 20-30 minutes from the terminal. Cross the highway, to the left look for the BCR bank on the corner and follow that road. Shortly after you pass Mosaic wine bar, go left up the hill, following the signs to Hostel Cascada Verde.
Or you take a taxi by the BCR for $4 (2000 colones).