In the following link you will find an update from the American Embassy, with a clear explanation of the new regulations for entering Costa Rica from different parts of the United States: https://cr.usembassy.gov/200829-travel-alert/
Briefly the main considerations, but it is important to read the full article:
The Ministry of Health expanded the list of states from which tourists can enter Costa Rica. As of September 1, 2020, U.S. citizen tourists who are residents of New York, New Jersey, Maine, Connecticut, New Hampshire, Vermont, Virginia, Maryland, and the District of Columbia may enter Costa Rica. As of September 15, residents from Pennsylvania, Massachusetts, and Colorado will also be allowed to enter Costa Rica. As of September 1, U.S. tourists from authorized states can arrive to Costa Rica via a flight with a layover in a non-authorized state or country. For example, a Colorado resident can fly from Denver to Houston to Costa Rica, as long as they do not exit the airport in Houston.
The Ministry of Health has also modified entry requirements from U.S. citizen tourists. As of September 1, U.S. citizens from authorized states wishing to enter Costa Rica must complete a digital epidemiological health pass, obtain a negative PCR-RT coronavirus test taken within 72 hours of their departure from the United States, and purchase travel insurance that covers accommodation in case of quarantine and medical expenses due to COVID-19. U.S. tourists must also demonstrate, via a valid driver’s license or State ID card, that they live in one of the authorized states. No forms of documentation establishing residency in these select states other than a valid driver’s license or State ID card will be accepted at this time.