Acapulco, Mexico (CNN) -- It's early in the evening and they're already on the streets looking for customers.
They are all very young, some still in their teens. One teenage girl wearing a tight, revealing, deep pink dress walks by while prying eyes follow her every move. At La Noria Street in downtown Acapulco, this is part of daily life. It's supposed to be illegal, but it's not hard to find underage girls offering sex for money here.
This is Acapulco's dark secret and the reason why the Mexican beach resort has gained a sad notoriety with tourists seeking children for sex.
Rosario Santos, who runs a shelter for street boys and girls called New Hope, says that customers are "mostly foreigners" coming to Acapulco on cruises or by plane.
"We have rescued children as young as 10," says the 52-year-old who has made protecting children her mission in life.
One of the children she rescued is Irene Lopez. The 20-year-old says she was only 16 when she got caught in the trap of prostitution after running away from an abusive home. "We would do things with them after making a connection," she says, sometimes in broad daylight too, often under the influence of drugs. To "make a connection" in the parlance of the street here means to pick up a customer for sex.
Lopez says her customers were all tourists, mostly from the United States. She would get 500 pesos, or about $42, per customer, but says that in some instances she was so high on drugs that she doesn't know what she was paid. "My mind was blank," she says.
It is an open secret that the main square in downtown Acapulco was the place to go for pedophiles.
Customers would wait at the square to make "a connection" with children providing sex for money, children's rights activists say. The square is sometimes known as "La Pasarela" which means "The Catwalk" in Spanish.
But some children's right activists like Rosa María Cruz Muller say things have improved dramatically in the last few years.
She and others have pressured officials to increase police presence at The Catwalk, while helping as many children as possible get off the streets.
Those children are taken into shelters, some run by the local government, where they find protection and a home away from drugs and the violence of the streets.
"Thank God we have seen a decrease of all that in the downtown square. Children used to tell me that people would pay them from $4 to $9 to do it. I would always tell them that it was not worth their life and their emotional and psychological well-being," says Cruz.
Melissa Monroy, who works at a shelter known as the Acapulco Children's Home, has repeatedly heard the same abuse stories. "These international tourists come here and abuse them (the children) and that is so sad. And we have many, many cases. Most of the cases here in this home are like that," says Monroy.
Sixty children live at the shelter where they not only get their basic needs met, but are also given psychological support and academic assistance. Most go to school and live a normal life. College students from the Acapulco area routinely visit the center to serve as tutors and mentors to the children.
Back at the "new hope" shelter, Irene Lopez is singing a worship song while some of the children join in. It's her way, she says, of trying to forget the dark life she used to live. "Thank God I now feel better. I have received a lot of support and they're helping me to get (drug) therapy," Lopez says.