GUANAJUATO, Mexico (AP) ― Pope Benedict XVI worked to build the future of Mexico’s church by reaching out to children Saturday as tens of thousands of teenagers streamed into a vast, shade-starved park to camp out overnight ahead of a gigantic papal Mass.

The pope reserved his only public remarks Saturday for a gathering of about 4,000 children and their parents massed in Peace Plaza in the city of Guanajuato.

“We’re excited to hear his words, not just for this moment, but to carry in our lives and to know God better,” said 17-year-old Fabiola Gonzalez, who traveled by bus with a group of 45 teenage girls from Guadalajara to the plaza. “We hope they will last more than this week.”

At the entrance to Guanajuato, Benedict received the keys to the city and then traveled by popemobile past faithful crowded along the cobblestone streets of the historic colonial city, which was the birthplace of Mexican independence and an armed uprising against harsh anti-clerical laws in the 1920s.

People packed the narrow streets, balconies and rooftops and cheered wildly even as it started to sprinkle. Children and teenagers ran through crowds as Benedict passed to catch another glimpse of him. At one point, someone handed him a bady through an open window of the bulletproof popemobile. He kissed the baby and an aide passed the child back.

As he left his residence in the late afternoon for his meeting with President Felipe Calderon in Guanajuato, Benedict went out of his way to bless dozens of babies handed up to him by their parents.

While such gestures are routine papal fare, Benedict seemed to zero in on the children in the crowd.

In his blessing, he was expected to refer again to the need for them to stay away from the drug-fueled violence that wracks Mexico.

“We young people are getting closer to the church and to God, instead of getting closer to drugs and violence,” said Juan Daniel Pacheco, 18, of Apaseo el Grande in Guanajuato state as he sought shade with his friends at one of the campgrounds that were quickly filling with faithful arriving for Sunday’s Mass. “We are young people who will be able to change Mexico.”

Benedict has taken up Pope John Paul II’s drive to reach out to young Roman Catholics, following in his footsteps by rallying millions of young faithful to join him for World Youth Days, the Catholic youth festivals held once every three years. The next edition is scheduled for Rio de Janiero.

He awoke to the pre-dawn serenade of two dozen youths from a Guadalajara church group who sang him a traditional folk song after getting as close as security would allow to the college in Leon where the pontiff is staying during his three-day visit to Mexico.

“We sang with all our heart and all our force,” said Maria Fernanda de Luna, a member of the group. “It gave us goose bumps to sing ‘Las Mananitas’ for him.”

The focus on youth fits with the Vatican’s drive to re-evangelize parts of the world where Catholicism has fallen by the wayside, trying to rally the next generation to embrace a faith that their parents may have abandoned. While Europe has certainly been Benedict’s focus to date, Mexico also has seen its number of Catholics fall.

“The Mexican church feels like it’s lost a few generations of Catholics,” said Joseph Palacios, a professor of Latin American studies at Georgetown University, citing the battles over liberation theology that drove many left-leaning Catholics away. To get back its numbers, the Mexican church is “moving forward with the new generation,” he said.

Yet as much as Benedict was receiving a rapturous welcome from young Catholics, his first full day in Mexico was not without criticism _ particularly concerning the church’s treatment of children and sexual abuse.

On the second day of the pope’s visit, victims of Marcial Maciel launched a new book containing documents on the Vatican’s alleged cover-up of sexual abuse of seminarians by Maciel, the founder of the Legionaries of Christ.

Alberto Athie, former priest and one of three co-authors of “The Desire Not to Know,” called on Benedict to publicly recognize the church’s responsibility for Maciel’s abuse.

“The church won’t fall. On the contrary, it will be reconstructed,” he said.

Of the 43.5 million Mexicans under age 20, 36.2 million are Catholic, or 83.2 percent, just under the national average. The largest group of Mexicans overall are children aged 5 to 9 _ a prime target for Benedict’s efforts to rebuild a church that has fallen victim to the same secular trends that have emptied churches across Europe.

Benedict will greet tens of thousands of young faithful on Sunday, when he celebrates Mass in the enormous Bicentennial Park.