I also live up here in the north of Costa Rica near Sandcruiser and there are some critical, time consuming issues to deal with when leaving the country in a Costa Rican registered vehicle. When you buy a car here the transaction has to take place with a lawyer (abogado) and a legal document is drawn up. The document has to be then filed with the National Registry (Rehistro National) for the official change of ownership which can take several weeks at best. After you receive the title with your name on it, you must get permission from the Rehistro National to leave the country in the vehicle. Another issue is that when a vehicle is in an accident or is issued a traffic citation, the violation is recorded into the rehistro national by license plate number, not drivers license. What this means is that if you want to buy a vehicle that has unresolved tickets or accidents, the title cannot be transferred into your name until the issues are resolved. Not to be a buzz kill, but its the facts. The current exchange is 520 colones= $1.00 so dont freak out when you see the prices.
http://supereconomicos.com/crautosindex.htm