the languaje is Mexican Spanish, but not the one you listen to in the streets. It's a bit overacted, too formal, too dramatic, a tad close to that of certain dramas or even soap operas -of the time being-. We Mexicans, regardless of social status, spice the speech up with no little amount of harmless cursing and insulting, totally absent in the movie, in fact probably in Mexican movies and TV until fairly recent times.
Yes, there are slight class distinctions between the servants and the guests/owners, but not in every case. Some guests' accent could sound less educated, and the servants accent in reality should have been more noticeable. The butler speaks with an educated accent but a high end servant languaje.