Those who wish to explore Costa Rica may find themselves able to move freely throughout the country, even without the assistance of a visa. Up to 90 days of unhindered traveling can be granted to individuals who have nothing more than passports.
How is this accomplished?

Costa Rica now offers blanket permissions to specific countries, allowing citizens to enter the Jaco, Los Suenos and other Central Pacific regions without visas. These countries include: the United States, the United Kingdom, Canada, France, Brazil, Greece, Argentina, Finland and Puerto Rico.
Why do these areas have immunity from the visa law? They've have reached good standing within Costa Rica and are supported by the National Board of Tourism, as well as the Embassy. They pose no security threats and have instead actively participated in trade or diplomatic matters. Their citizens, therefore, are extended certain courtesies.
To see if you qualify for passport entry, visit the Costa Rican Embassy’s official site (choose the Spanish or English version).