What exactly do you think "cartel activity" looks like? The fact that some random international tourist didn't witness any overt "cartel activity" does not remotely imply that it is not a problem in Mexico. These cartels have been in open war with the government for decades, police and military forces are regularly compromised, and frequently the cartels form defacto local governments when they take over towns. Pablo Escobar was one of the wealthiest people in the world when he went to war with the colombian government, mexico has similar issues.