In Paraguay, most people speak a mixture of castellaño (Paraguayans’ preferred term for Spanish) and Guaraní, which is called jopara. “Jopara” means “mix” in Guaraní. When I think of jopara, I think of Spanglish; it’s the same idea, just with different languages. Basically, when talking you can use Spanish or Guaraní syntax and use a combination of Spanish and Guaraní words. Put simply, you are conversing in two languages at once, and there’s no right way to do it. Some people use more Guaraní, some people use more Spanish. It just depends on the person, the topic, and the context.
You can get by in Paraguay speaking castellaño, most teens and adults will understand you and be able to respond in castellaño. But, as you get more rural or if you want to talk to kids or older people you have to know more Guaraní. If you want to understand what people are saying to each other you have to know Guaraní. If you want to understand what the guys are yelling at women as they walk down the street or what the old ladies are joking about over terere, you better know Guaraní.
When I was in training, my Peace Corps teachers always said Guaraní is the language of the heart in Paraguay. They explained that to make deep relationships and to really excel here you have to learn Guaraní. But, in my experience, Guaraní is as much a core of Paraguayan identity as it is a language of the heart.
Paraguayans are very proud of Paraguay. They may criticize small aspect of Paraguayan culture or their government but they will never question Paraguay. They are proud of and enjoy their tradition food, dance, music, terere, mate, and crafts. Coming from the US, where individuality is so central to most people, the uniformity in Paraguay is unfathomable. Everyone seems to listen to the same 20 songs, eat the same 7 foods, and do the same thing in their free time. To me, Guaraní is the summary of everything that Paraguayans feel makes them Paraguayan.