Opinions vary.
The thing here is, you get NONE of this in the resort towns. Playa Del Carmen, Cancun, Cabo, etc are all in their own little world. If you stay at the resort or near it you will be fine. My wife and I love Mexico. It's less than a 3 hour flight from Denver and the ocean/beaches are amazing. Not to mention if you stay at a nicer property you can get all the food and top shelf booze you can drink for cheap.
All this said, I would not go to Mexico city or the border towns if you paid me!