Wikipedia
Jopará ( or Yopará is a colloquial form of Guaraní spoken in Paraguay which uses large numbers of Spanish loan words. Its name is from the Guaraní word for "mixture."
The majority of Paraguayans, particularly younger ones, speak some form of jopará.
Since 1992, under the Paraguay's Ministry of Education and Culture (MEC) Act, Guaraní in its "pure form"—different from the day-to-day speech of jopará—has been taught in schools. This led to contradictory opinions: some say that teaching pure Guaraní is the best means to preserve the language's integrity, while others argue that how Guaraní is taught differs greatly from how it is commonly spoken.
Some Spanish words, when put in a sentence mixed with Guaraní, have a different meaning than that of standard Spanish.
The relative amount of Guaraní or Spanish used in speech varies depending upon the birth of the speaker, the place where he speaks, with whom he or she is speaking, the topic of discussion, and how he or she wants their meaning to be interpreted. Generally, the rural and older population tends to use more Guaraní, while the urban and younger population uses more Spanish - the rural and older population understands more Guaraní and the urban and younger more Spanish. General and every-day conversation is more suited to Guaraní, while technical and specific or formal conversation is more suited to Spanish. Guaraní can be interpreted as more "Paraguayan" while Spanish can be interpreted as more "sophisticated."