Follow the way back to San Jose (HERE the details from the road to Tortuguero).
- Boat Tortuguero - La Pavona (11:00)
- Bus La Pavona - Cariari - take a seat and wait they don't have real arrival hours, it depends on when it comes from Cariari based on the departure hours 
- Cariari - San Jose - there are several buses (as before you need to walk to the new bus station)

Maybe best to go before November to have the chance to see the real Turtle experience, but even so Tortuguero was a nice stop. 

We arrived there around 6 PM, went to the place we were sleeping "Cabinas Tortuguero" where we booked a one night stay. The owner was extremely nice gave us some good advise on how to book the tour but even so it is hard to recommend it. Now maybe this is not an important aspect to everybody, but the ants going around my bed did not make me very happy. The price was 35$ per night for a triple room with private bathroom. 

The route you need to follow, possible in 1 day would be:
Drake - San Jose - Cariari - Pavona - Tortuguero 

Before I start: THERE are NO BANKS in Tortuguero so get money in advance