We really didn't start to learn how to give addresses this way until we started giving addresses to foreigners who had no way of knowing where the Strangler Fig is, where Matute Gomez' house is, what Pulperia La Luz is and which one of the 100 churches in San Jose they are talking about. While on the panamerican highway, the road is in generally good condition by Costa Rican standards. For the most part the highways are two lane highways. There are the inevitable pot holes, and the lanes are narrow. For the most part roads have many curves, be prepared for big buses and trucks passing on blind curves.
Fog is also quite common on some of the mountain passes.
During the rainy season landslides are often seen both on the highway and off. The roads that branch off of the highway to go to Monteverde or the beaches for instance vary in quality. There is everything from gravel and dirt roads that are passable to really difficult to negotiate back country roads. It is best to ask your car rental agent, the hotel you are going to, or your travel consultant about the conditions of the road before you head out. Many foreign drivers complain that the roads are inadequately signposted.