I hope this contributes a little. I’m not a native Spanish speaker, so I can really tell when someone speaks differently than what I’m accustomed to. I can even use my wife’s immediate family as they seem to scale the range of social classes in Mexico. I can only fairly use my wife, below, as my standard, since I live with her and her manner of speaking is that to which I’m most accustomed (similarly, if you’re from Boston I’ll think you talk funnily).
Dad: grew up dirt poor, and didn’t finish elementary school; he’s ranchero and so speaks. For the most part he speaks rather clearly; the most notable difference is he’s prone to slur the ends of “-ado” words, such that “congelado” comes out “congelau.”
Mom: similar circumstances with less education. Speaks clearly, but is prone to say things like “rumpido” instead of “roto” (“broked” instead of “broken”). His accent is often kind of like the Mexicans sound on Speedy Gonzalez cartoons, but maybe not as strong.
Wife: well, for this exercise is the standard. Aside from her first seven years of life living on Manzanillo beach, she’s a product of La Salle from elementary through university, and I hear her correct a lot of Spanish grammar. I imagine her normal speech would be some type of “standard Guanajuato Spanish.” Early life started dirt poor, so she has first hand experience living lower class as well as upper class. She’s a dentist.
Oldest Brother: similar to my wife, and speaks very clearly and understandable. Didn’t start the private schools until intermediate school, and got his medical degree at a government school.
Next two sisters: Don’t seem to speak as finely as the two older brothers, but weren’t as dedicated in school. One came out a dentist and works for the state. The other sells Mary K cosmetics. They remember a couple of years of not living so nicely.
Next brother and sister: born into a wealthy home. The sister speaks very clearly and on the snobbish side (accountant). The (baby) brother qualifies as “un junior” in every respect. He speaks very clearly and educatedly when he needs to, but normally kind of “fresa.”
In Leon in general the people speak clearly, with the credit definitely going to the younger generation. At normal neighborhood stores and restaurants you can really tell the difference in the clarity of speaking among the generations, but at the more upscale places everyone speaks clearly and well, even the older.
In the Federal District, it seems to be a random mismash of whoever you run into. But the movies I’ve seen filmed there are easy enough to follow.
In Cd. Juarez, everyone speaks about as fast as the Cubans and I lose them. (generalization)
In Cuba, everyone speaks fast and seems to clip the ends of their words. (generalization)
I don’t know what the deal with the Pueto Ricans is – they sound like they have potatoes in their mouths. (generalization)
When I hear myself recorded in Spanish, well, I sound gringo to say the least. But at least I’m fluid and understandable.
The news from Mexico and Florida is pretty clear, but probably for the same reasons most of our news is accent-less regardless of where you are.
One of the soap operas from Columbia has everyone speaking really well, but with Columbian vocabulary. But a “real” Columbian friend-of-my-wife speaks bien rapido and everything comes out sounding like sh----. I don’t mean the expletive, but the sound: “Vamosh a irsh a la tiendash.”
Ive only seen a couple of Spanish-from-Spain movies, and they sound cute and understandable, but distinctly different.
My wife says that when the Olympics were in Spain, all of the coverage in Spanish disappointed her because it was, for her, some crappy non-standard Spanish that was difficult to understand, and she felt the coverage should have been in “Standard Spanish” (whatever that is).