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.
This is often true, so try to get hold of a decent road map and ask locals if you are not sure. Costa Ricans are nearly always able and willing to help. Citizens of all nations require at least a passport to enter Costa Rica. This is not to say that if you wait until two months prior to your traveling time you won't be able to make reservations, you will be able to find space, it just may not be exactly at the hotels you originally wanted, and if a guide is important to you it may difficult to get one. You probably have some expectations as to how this trip will be.