Student visas are not so hard to get if you enroll in a local university and work for a degree, or would like to do a semester abroad arranged through a university you are enrolled at. But I would not even bother going to stand in line at immigration if you are just going to take a few Spanish courses at a local academy. Even Spanish courses offered by local universities for foreigners would not be qualifying you for a student visa.
Here are the requirements posted on the website of Costa Rica's US embassy in D.C.
www.costarica-embassy.orgTemporary student visa (one year or less)
Temporary permits are extended to foreign students, registered in public or private education centers recognized by the State, for the duration of specific academic periods. This permit does not allow students to work. The application should be done at Migration in Costa Rica, and the student will require the following documents:
* Passport valid for at least 6 months and certified copy of all its pages.
* Request letter from the student (in case of students under 18 years old, this request should be signed by the parents) to the Temporary Permits Department, Immigration Costa Rica (Departamento de Permisos Temporales, Dirección General de Migración y Extranjería). In this letter the student should state his/her name, civil status, nationality, passport number, place of residence, occupation, etc. Include the name of the education center where he/she plans to study and a place to receive notifications (address, phone, fax in Costa Rica).
* Confirmation of enrollment in an accredited School/University.
* Fill out the Immigration form, which can be obtained at the Information Desk in the Immigration Office.
* A letter from your sponsor (Guarantee letter), stating that he/she will be responsible for your actions during your stay. Your sponsor must be a Costa Rican citizen or a permanent resident of our country. Include a certified photocopy of the ID of the sponsor.
* Show proof of sufficient funds available for self sufficiency during entire proposed study.
* Fingerprints (for students from up to 10 years old). You should have them taken at the Archivo Policial of the Ministry of Public Security. Bring passport and two pictures.
* 4 passport sized pictures (recent)
* After permit is approved, the student should make a US$100 guarantee deposit.