The streets of Leon were lined with people waiting to greet Benedict, and the city's cathedral was decorated for the visit, KTRK-TV, Houston, reported.
Speaking to reporters onboard his flight from Rome, Benedict said drug traffickers' "false promises" hide the evils of money worship, the Los Angeles Times reported.
"It is the responsibility of the church to educate consciences, to teach moral responsibility and to unmask the evil, to unmask this idolatry of money which enslaves man, to unmask the false promises, the lies, the fraud that is behind drugs," the pope said before his visits to Mexico and then Cuba.
He called on the island nation to find "new models" for society.
"Today it is evident that Marxist ideology in the way it was conceived no longer corresponds to reality," he said. "In this way we can no longer respond and build a society. New models must be found with patience and in a constructive way."
A Mexican man who traveled to Rome earlier asked Benedict to remember victims of such violence during his visit to Mexico.
"I have come to Rome, Benedict, to ask that in your visit to Mexico you embrace [the drug-war victims] ... as the Father embraced the pained and murdered body of Christ," Mexican poet and peace activist Javier Sicilia said at the Vatican as he delivered a letter to the pope.
Sicilia's son, Juan Francisco Sicilia Ortega, 24, was one of seven people killed by alleged Mexican drug gang members March 28, 2011.
After burying his son, Sicilia said, "Poetry doesn't exist in me anymore."
An estimated 50,000 people have been killed in drug-related violence in Mexico in less than six years.
The country mobilized a massive security force, including more than 13,000 federal, state and local police officers, as well as soldiers, ahead of Benedict's arrival at Guanajuato International Airport outside Leon, officials said.
Guanajuato is a north-central state between the country's arid north and its more lush south. It is about 94 percent Catholic -- the highest percentage in Mexico.
President Felipe Calderon and the papal nuncio, Christophe Pierre, were to meet Benedict at the airport, and traditional songs including "Cielito Lindo" and "El Son de la Negra" -- often called Mexico's second national anthem -- were to be performed, Mexican officials said.
The last time Benedict went to Latin America was in 2007, when he visited Brazil for a Latin American bishops conference.
His predecessor, John Paul II, visited Mexico in 2002.
In Guanajuato, Benedict was to hold several large open-air public masses, meet with Mexican bishops and discuss religious policy issues with Calderon six days before the start of a presidential campaign.
The church has denied any political overtones to the pope's trip.
As many as 300,000 people were expected to gather for a Sunday mass, where temperatures were expected to be in the mid-80s Fahrenheit.
The 84-year-old Benedict was to fly to Cuba Monday and be met by Raul Castro in Santiago de Cuba.
His trip to Cuba is officially timed to celebrate the 400th anniversary of the discovery of a statue of Our Lady of Charity, or the Virgin of Charity, the patroness of Cuba, admired even by Cuban communists as a symbol of nationalist unity, The Washington Post said.
Many analysts see the pope's Cuban visit as a demonstration of support for Cardinal Jaime Ortega, who is being criticized by human rights activists because he asked police to remove 13 dissidents who were occupying a Catholic church in Havana, the Post said.
The incident is one of several reported this week involving Cuban security forces, including the arrest of members of Ladies in White, or Damas de Blanco -- a group that routinely holds silent protest marches in Havana. The U.S. government and the U.N. National Security Council condemned the arrests but neither Ortega nor the Vatican has commented publicly, the Post reported.