I concur, I live right on the border here in Brownsville, Texas and have made the trip south to Quinta Roo a few times many years ago. It used to be something done without a second thought, now it is not something I'd do at all. The organization I work for owns two field stations about 6 hours south of here in the northern-most cloud forests of Mexico. We've been traveling there for the past 60 years, taking highschool and college kids down on field trips. We haven't visited in over 5 years.
Our neighboring state of Tamaulipas has been the epicenter of violence in northern Mexico for the last few years. Countless hijackings, kidnappings, and murders. Many which have occurred along major highways where the cartels setup their own checkpoints. If you must go, get to the bridge as early as possible--before day break--so that you can get all the required paperwork done and then just focus on getting south to Veracruz as fast as you possibly can. Once you're down towards the southern Gulf, things calm down considerably and the rest of the trip should be a breeze. Don't dabble on the way.
Odds are, you'll be fine, but you're taking a considerable risk that if something happens, it could be life threatening. What kind of vehicle will you be taking? You may find at the border crossings, while filling out all the appropriate costumes forms, that you're approached by members of the various cartels inquiring where you're headed and requesting a fee to insure safe passage through their "territories." I've heard mixed reports of this, most people pay it, but it's questionable as to whether or not it's a real thing or just individuals taking advantage of the situation...
I love Mexico and I still visit regularly as many parts--such as the Yucatan peninsula--are very safe, I just don't drive anymore...
