I can't see why you'd want to vacation in any of those places. It may be safe for you or I, but kids that age are stupid. They can get themselves into trouble especially when alcohols involved. The Sonora state is listed as a level 3 due to crime and kidnappings.
I'm pretty travel savvy and I wouldn't wander around any of those cities alone at night.
I get that. I mean, I'm DONE going to Mexico. I won't even take a cruise that goes there. I was just pointing out that it's a LONG border, and not all border cities are equal in terms of risk.