You can be arrested for:
• Disturbing the peace or being a public nuisance.
• Drinking in public.
• Fighting.
• Nudity or immoral conduct.
• Use, production or sale of false documents.
• Possession, introduction, or use of any weapon without a permit.
• Possession, introduction or consumption of restricted drugs. (Note: Most drugs that are restricted in the U.S. are also restricted in Costa Rica.)
• Drunk driving or driving under the influence of drugs.
• Causing an auto accident or injuring someone.
What you should do after you are Arrested
A U.S. consular officer cannot get you out of jail, since you are subject to Costa Rica’s laws, but we can monitor your condition while incarcerated. If for some reason you get arrested in Costa Rica and you end up in jail in Costa Rica. The first thing you should do is tell the police or official to contact your country's Consulate or Embassy in Costa Rica. The Consulate, when notified by local authorities of the arrest of an American citizen, will visit the detained person within 24 hours and at least once every quarter during his incarceration. Upon learning of an American’s arrest, the Consulate seeks to visit the citizen to insure there has been no abuse or mistreatment, inform him of his right to legal counsel, provide him with a list of attorneys from which he may select legal counsel at his own expense, and to obtain personal data which will assist the Consulate in communicating with family or friends who may be able to provide financial and other assistance.
The Consulate can do the Following:
1. Provide a list of local attorneys or contact an attorney selected by the accused.
2. Contact relatives or friends to notify them of the citizen’s case, if authorized by the prisoner.
3. Relay requests to family and friends for money or other aid.
4. Write to relatives about the citizen’s well-being.
5. Accept funds as a trust fund deposit and dispense them as instructed by the citizen or the remitter.
6. Work with prison officials to ensure fair and humane treatment consistent with that granted to Costa Rica nationals and ensure Americans are afforded due process under Costa Rica law.
7. Protest mistreatment.
The Consulate can not:
1. Represent a U.S. Citizen at trial, give legal advice or pay legal fees and/or fines with U.S. Government funds.
2. Intervene with the due process of law.
3. Provide medical treatment except in cases of dire emergency.
4. Run errands for the prisoner.
Proof of US Citizenship
In order to receive consular services, each prisoner must prove that he is a U.S. citizen. This can be most easily accomplished by presenting to the visiting consular officer or having relatives send the Consulate a certified copy of a U.S. birth certificate and original identification, or U.S. passport, certificate of U.S. citizenship or U.S. Naturalization certificate.
Transfer Sentence to Home country
Under U.S. law ( 18 U.S.C. §§ 4100-4115 ) foreign nationals convicted of a crime in the United States, and United States citizens or nationals convicted of a crime in Costa Rica, may apply for a prisoner transfer to their home country.
http://www.costaricaninsider.com/costa-rica-arrest.html