Costa Rica is a democratic republic, headed by President. Government is also headed by president. President and Legislative Assembly (parliament with 57 deputies) are elected once every 4 years. President unites executive power and he appoints cabinet of ministers. President is assisted by two vice presidents; one of them is also represented in cabinet. In 1969 Assembly ratified constitutional amendment, which imposed limitations on presidency and deputy only for one term. Nevertheless deputies can be reelected, while president got such right only in 2003 after amendment was recognized to be anti-constitutional. Such change allowed Oscar Arias to be reelected in president elections of 2006. Offices of Comptroller General of the Republic, the Procurator General of the Republic and Ombudsman are not controlled by government.

Executive central...

In Costa Rica provincial legislatures are absent and provincial agencies experience wide autonomy in their activity: nationalized banks, monopoly on telecommunications and electrical power enterprises, social services.
Making a conclusion it's important to not that in close future Costa Rica will not experience any remarkable political changes. Balanced political power, educated political elite and absence of politics among militaries have created prolonged stability. Even constitutional changes in lections legislature will not affect much politics of the country with its distributed spheres of influence among political elite.

Reference: http://www.worldheadquarters.com/cr/government / http://experts.about.com/e/p/po/Politics_of_Costa_Rica.htm