Costa Rica is actually pretty well off. It has some poverty to be sure, but its population is small and the country is very safe. Most roads have names, but many roads have the same names, and there's no consistent numbering scheme.
Also, outside the capital, there's really not much of a need for signs: Costa Rica is small and very tourist-friendly, so asking for directions is easy (English is very common and taught in a lot of the schools).
During my vacation in Costa Rica, I found the Ticos friendly, but in my experience they give terrible directions! Everything was "about 8 km straight ahead" with every Tico that I asked, even when it was actually 50 km :) Language wasn't an issue because I'm a native Spanish speaker (funnily enough, many Ticos tried to talk to me in English even when I told them I spoke Spanish natively! Though to be fair I encountered this phenomenon in many tourist-oriented countries).
I just find it funny, of course it's not a real problem. But note I don't come from a first world country, and in fact my first language is Spanish, like the majority of my fellow countrymen.
So I found it very funny that my average conversation when asking a Tico for directions went something like this:
"Hola, ¿me podrías indicar dónde queda $LOCATION?"
"Of course sir! First you take this route--"
"Perdón, hablo español."
"Suuure, sir. As I was saying..."
Also, outside the capital, there's really not much of a need for signs: Costa Rica is small and very tourist-friendly, so asking for directions is easy (English is very common and taught in a lot of the schools).