Flying to Limon
There is no airport in Puerto Viejo or Manzanillo but you can fly from San Jose to Puerto Limon and then continue on bus or Taxi to Congo-Bongo Manzanillo (a little more than an hour further). The 2 Costa Rican domestic airlines use small turboprop planes.
Nature Air flies from San José's Pavas Airport (this is NOT the main international airport) . Flights are not always daily though so check the Nature Air website for current schedules.
Sansa Air flies from a separate terminal at the main international airport San Jose . Although their route map shows San José to Puerto Limon flights, no flights have been scheduled yet but check the Sansa website for current information.