I've never been to any of the resorts on the coasts, but the abject poverty throughout Northern Central from the Laredo/Nuevo Laredo border crossing (et al.) is like nothing we've ever seen here. Bleak is an understatement when it comes to the smaller towns and cities whose roads are only double lane, dirt road ruts in the desert and homes the size of our backyard sheds built either from homemade abode, or cinder block with corrugated fiberglass for a lay over roof.
Some of the houses are so isolated you won't see another one for miles even though the terrain's flat. Many of the houses don't even have window glass and only have a sheet or blanket for a front door. Thankfully (?), they get very little rain; a double-edged sword since there's no irrigation and most crops won't grow, no grass to feed livestock in a lot of places. Some families do keep a goat tied up on a stake for milk and meat, but keeping the rattlesnakes, lizards, spiders and other desert dwellers out and away from the family and the goat while sweeping packed dirt floors is a full time job.
While the coastal regions are simply gorgeous (from the pics and friend's descriptions in my case), and some of the more well-known cities aren't as impoverished and do have a little better standard of living (still very different from ours, though), the majority of Mexican families live a harsh existence. I personally love it there b/c of the people, but the first time I went was also the first time in my life I was thankful to pay my taxes.