The dreaded deportations that would surge under Trump

The bell rings at the gate of the Tijuana border post as US agents return 12 Mexicans home with their belongings inside paper bags and backpacks.

Such deportations occur on a regular basis, but they could increase exponentially if Donald Trump ? set to be confirmed as the Republican Party's presidential candidate next week ? wins the election in November and makes good on his promise to expel millions of undocumented immigrants.

At the San Ysidro border station, most of the deportees look on dejectedly, several of them lacking any identification, as a Mexican agent unlocks a metal door and interrogates them to make sure they are really Mexican.

"Where are you from?" he asks. "What's near that town? Do you have 'pisto?'"

That's a trick question. "Pisto" is Central American slang for money, a term not used in Mexico.

After they pass the improvised citizenship test, the migrants walk through a wooden door into the El Chaparral repatriation center.

"Welcome home," reads a sign in Spanish.

"Goodbye America!" says a migrant looking back wistfully.

- 'I will go back' -

Some 30,000 of the 207,000 Mexicans deported from the United States last year were sent back through the San Ysidro gate ? which separates Tijuana and San Diego, California ? according to Mexican government figures.

Children, unaccompanied teenagers, pregnant women and elderly people are taken through the gate. Some are returned shortly after crossing the border illegally, others have unsuccessfully tried passing the border bridge with fake IDs or had lived in the United States for years.

Trump has angered Mexicans by vowing to build a massive wall to block such illegal crossings by people he has described as "rapists" and drug dealers.

Juan Carlos, a 35-year-old day laborer from the northern state of Sinaloa who was among those recently deported, suggests another idea for Trump.

"It would be better for this gentleman to help so that we could get paid better here and not go over there," he said.

Juan Carlos, who declined to give his last name, was wearing a shirt still covered with dirt from hiding in the hills when he snuck across the border.

Now he was eating a sandwich provided by the Mexican authorities as he sat in the El Chaparral waiting room expecting a repatriation document along with others.

He planned to make another attempt to cross the border.

"They threatened to send me to prison if I returned," he said, adding, "I will go back."

Javil Cortez, 28, illegally crossed the border because he wanted to "be someone in life."

The farmer had hoped to improve the lives of his four children in the violent western state of Michoacan. Unlike Juan Carlos, he planned to go home.

- Crushed 'Dreamers' -

Millions of people have been deported from the United States in recent years. Latino advocates call US President Barack Obama the "deporter-in-chief."

But Obama has also sought to spare millions from deportations in a program recently blocked by the Supreme Court.

For his part, Trump has vowed to deport the 11 million undocumented migrants in the United States, most from Mexico.

"As long as I can remember, there has been anti-Mexican feelings, xenophobia," said Nancy Landa, who migrated to Los Angeles at the age of nine but was deported through El Chaparral 20 years later because she lacked proper documents. "It's a problem of ignorance about the reasons why people migrate."

Landa, who earned a degree with honors in business administration in California, is among two million so-called "Dreamers" -- undocumented migrants who arrived in the United States as children.

She is among 200,000 Dreamers sent back since 2009 to a country she didn't know, with no Mexican documents.

"It's complicated. People noticed from my Spanish that I wasn't from here," said Landa, who initially worked in a call center thanks to her English skills and now lives in southern Mexico.

"For a while, I felt that there was a stigma attached to a person who was deported because they think that you have a criminal record," she added.

Deportations have split up many families. Border cities such as Tijuana have become refuges for those who have been expelled but want to stay close to relatives remaining in the United States.

Yolanda Varona, 49, was deported in 2010 after living in California for 17 years with an expired tourist visa. She left behind two sons.

Varona founded the Dreamers' Moms group. Every Thursday, she and other deported mothers and fathers ? many with US-born children on the other side ? meet to talk and cope with their pain.

Trump is not popular in the room.

"I think that this gentleman is sick," Varona said. "Not all Mexicans are thieves or rapists or ignorant. I think that we have helped the United States become such a powerful nation."

But around half of foreigners deported by the United States are criminals, according to the US Homeland Security Department.

Mauricio Hernandez-Mata was deported in 2010 after serving prison time for drugs and illegal gun possession.

But the 34-year-old Mexican, who was raised in San Diego, said he deserved better treatment after his US military service in Afghanistan in 2004-2005.

"Everything I did was from the heart," he said. "My actions must be taken into consideration."