WARNING: The U.S. Department of State warns U.S. citizens about the risk of traveling to certain places in Mexico including Tamaulipas due to threats to safety and security posed by organized criminal groups in the country. U.S. citizens have been the victims of violent crimes, such as kidnapping, carjacking, and robbery by organized criminal groups in various Mexican states. This Travel Warning replaces the Travel Warning for Tamaulipas, issued April 13, 2015, to update information about the security situation and to advise the public of additional restrictions on the travel of U.S. government (USG) personnel.
As of April 2011, Tamaulipas has become very unsafe even for Mexicans. The big problem now is the cartel wars (CDG, Z) that are terrifying all Tamaulipas. Traveling north to south has become very dangerous.
The San Fernando area (around 100 km from the north) is one dangerous spot these days. In this region was the discovery of an illegal graveyard where they found more than 100 bodies, some of them were slaughtered with cruelty by the Z cartel. So not visit Tamaulipas now. If you really have to, take some measures not to draw attention from drug cartels (no fancy clothes, not too much money, etc).