Travel.State.Gov
Click the link above for the U.S. Government Travel website for up-to-date travel documentation information.
The following excerpts are for your convenience and are subject to change at any time. Please refer to the link above.
Air Travel
All individuals, regardless of age, must have their own passport when traveling internationally by air.
Costa Rica
Visit the Embassy of Costa Rica in the United States website for the most current visa information. For entry into Costa Rica, you must present both a valid passport and either a round-trip ticket or proof of onward travel to another country. Because of possible fines levied by Costa Rican Immigration, many airlines will not permit passengers without proof of return or onward travel to board flights to Costa Rica unless they have Costa Rican citizenship, residency, or a visa. Costa Rican Immigration now also requires that you be able to demonstrate financial capacity of at least USD$100 per month while you are in Costa Rica as a tourist. When you leave Costa Rica, you will have to pay a departure tax of USD $29.
Passports should be in good condition. Costa Rican Immigration may deny entry if a passport is damaged in any way. Costa Rican authorities may permit U.S. citizen tourists to stay up to ninety (90) days, but are not required to do so; shorter lengths of stay of thirty (30) to forty-five (45) days are also common. To request an extension, you must submit an application for an extension to the Office of Temporary Permits in the Costa Rican Department of Immigration. Extension requests are evaluated on a case-by-case basis. Tourists who overstay the period of stay authorized by Costa Rican authorities without receiving an extension may experience a delay at the airport when departing, are subject to deportation and/or a fine of USD$100 for each month of overstay, and may be denied entry to Costa Rica on future visits.
El Salvador
To enter El Salvador by air or sea, U.S. citizens must present a current U.S. passport and either a Salvadoran visa or a one-entry tourist card. There is neither a requirement for the U.S. passport to be valid for a specific period of time nor for it to have a specific number of blank pages. The tourist card may be obtained from Salvadoran immigration officials for a USD$10.00 fee upon arrival in El Salvador at an airport or seaport.
Nicaragua
You must have a valid U.S. passport to enter Nicaragua. Although there is a bilateral agreement which waives the six-month passport validity requirement applicable to many countries, U.S. citizens should ensure that their passports are valid for the entire length of their projected stay in the country before traveling. U.S. citizen visitors must have an onward or return ticket and evidence of sufficient funds to support themselves during their stay. U.S. citizens do not need a visa; however, a tourist card must be purchased for USD$10 upon arrival.