Slang is often referred to as “Street” or Colloquial Spanish.

If your goal is to speak the language fluently and understand native speakers, you should study the expressions I have listed below.

Hablar por los codos – to be very talkative.
Vender gato por liebre – to cheat or deceive.
Meter la cuchara – to meddle or to butt in to a conversation, put in two cents worth etc.
Como para chuparse los dedos – delicious or finger licking good.
Hacérsele agua la boca – to make your mouth water.
Andar de fiesta or andar de parranda – to go out partying or paint the town red. In Costa Rica they also use Andar de manteles largos.
Media naranja – spouse, better half.
Andar para arriba y para abajo – go all over the place
Estar limpio – to be broke

Tiquismo of the week: Cascarudo is a shameless person in Costa Rica.