This is a Pixar movie set in Mexico. When Mexico or Latin culture in general gets depicted in Hollywood, it's usually a sad caricature of the real thing. Two recent high-profile shows come to mind:
Breaking Bad, one of the best TV shows ever, does a terrible job of this. The main bad guy is supposed to be from Chile (???) and his Spanish was beyond terrible. Everything else was about the same.
- Narcos, a TV show filmed in Colombia about a Colombian drug lord, chose a Brazilian to play Pablo Escobar. You can tell he tried, but his Spanish is off in an Uncanny Valley kind of way. There are other questionable casting choices.
In a refreshing contrast, Pixar seems to have done it's homework. The clips look and feel like Mexico. And whenever a character says something in Spanish, it sounds like a native Mexican Spanish speaker. Looks great and at the same time very respectful to the culture. How refreshing!