This week while I was working on the Tour Operator office we had to help two different couples of young travelers with directions on how to get to Cahuita by Bus from Golfito, The first couple were Canadians from Quebec, so it was very helpfull for them that our Staff speaks french and the other couple were French, I gave them both the same directions and they arrived great to Cahuita.
TOTAL DURATION OF THE TRIP: Around 10 hours.
APPROXIMATE COST: $25
First, the only company in Golfito that goes to San José is called TRACOPA, their office in Golfito is located in towncenter, on the main street just in front of the Fire Station, there you can get a ticket to San José for around $15, you can check on their site for updated schedule:
That TRACOPA bus will arrive to Plaza Viquez in San José, from that Bus Terminal you will have to walk around 30 minutes to get to MEPE Bus Terminal, or take a Taxi, MEPE is the name of the company with departures to Cahuita.
Here's a map that show you how to get from one terminal to the other :
Then when you arrvie they have buses leaving to Cahuita every two hours