Yes, they speak Spanish in Costa Rica. In reality you may be exposed to a variety of dialects. My list of confusing and entertaining Spanish language as it is locally used:
If you have learned some Spanish you might have the mistaken idea, corroborated by dictionaries, that it means "tomorrow". Most confusing when used as an answer to when something will be done. In reality it means "not today" and possibly it means "never".
Literally this means "now" but in reality it means "sometime before tomorrow". There is a gradation to ahorita which is nearer in the future and ya, which means "right now", but that is a little harsh and should be used only with some added politeness such as a smile and por favor.
Two simple words that will give you no indication of their deceitful nature. It is usually heard as an answer to a question of how much something is. The answer, tamaño poco, sounds like "a small quantity" while in reality it means anything from "quite a bit" to "I don't really know but probably more than you would think". You can live in Costa Rica for decades before figuring this one out by yourself.
Seems to mean "enough" but no! it means "a lot", actually it is one step up from tamaño poco in quantity.
This will be the first idiom you will learn. It means anything from "great" to "fine" and "excellent". Use it a lot and you will put a smile on people's faces.
The polite form of "you" normally used when addressing strangers and people of higher rank and generally as a sign of respect. Strangely enough in some areas it is also used within the family, even by parents to their children.
No, it doesn't mean "daddy". It is used mostly by parents addressing their young son.
Literally this means summer. In Costa Rica it indicates the dry season from December through May, which is winter and spring for most foreigner. Also, any day that is sunny, no matter what time of the year can be called verano.
In the dictionary you will find this to mean "ugly". However, that sounds much stronger than it is usually meant. The word feo is much weaker than the word "ugly". It is also used in surprising cases, such as when food tastes bad or in case of bad behavior.
This word is much stronger than the word "stupid" that we use all the time. Costa Ricans therefor hardly ever use it. So don't call someone or someone's behavior estupido. You may be better off with tonto.
The first time someone tried to sell me seven manzanas I was really puzzled. Why would anyone want to sell me seven apples? And why would they cost $70.000? Well, a manzana is also a land measure in Costa Rica. It is about 1.73 acres or 7000 square meters. If you do any travelling around by yourself you will hear this word because half the land in Costa Rica seems to be for sale.
This is another term for "one block", or the distance from one side road to the next. This may be far less or far more than the actual 100 meters that you would expect. When you are asking for directions you will hear this term. In a similar vein cincuenta metros is "half a block".
This means "to have a cold", it has nothing to do with constipation.