A combination of US dollars and credit/debit cards is ideal, it’s best to bring notes in good condition and lowe r than 100 USD. Traveler checks are not a good idea. Cards are widely accepted but smaller stores or street sellers may only take l ocal cash. There are ATMS along the way. Check with your bank to make sure your card will work internationally.
How much you need will depend on your spending habits. You will need to pay for some meals ($10-$20 per meal), drinks, souvenirs and tipping.
If you felt your local guides and drivers did an outstanding job, tipping is appreciated. It is customary in Latin America to tip service providers such as waiters, at approximately 10%, depending on the service.
The Departure Tax in Costa Rica is $29. This needs to be paid at the airport using US or local cash or any major credit card. Pay this tax before going to the airline counter. Check with your airline if this fee is already included on your flight ticket.