It is a criminal offense to drive under the influence of alcohol in Costa Rica. Citizens and residents will have there license suspended and their car confiscated, if they are caught driving with more than 1 beer. If you are a non costarrican, your license will not be suspended, but you will get a considerable ticket and the car will be confiscated.
We recommend that if you are going to drink do not drive, get a designated driver or get a taxi. In most tourist areas, the road police will always show around. So do yourself a favor, do not drink and drive while you vacation in Costa Rica.