You may use dollars most anywhere in Costa Rica. The local currency is colones. The exchange rate varies… today it is 555 colones is equal to $1. Popular denominations and dollar equivalents are: 1000c =$1.80 , 2000 c = $3.60, 5000 c = $9.00 and 10,000 = $18.00
Your bank debit or ATM card works fine in the ATM’s (cajeros automáticos) but the closest bank is in Jicaral… about a 45 min drive) The local markets (mercados) take credit cards with your identification.