By David Alire Garcia

NOGALES, Mexico (Reuters) - Donald Trump's election victory and his plans to crack down on illegal immigration is so troubling for the groups of men gathered just south of a rusty, towering fence on the U.S.-Mexico border that some are even considering going home.

For most poor Central Americans and Mexicans at travelers' shelters in the desert town of Nogales, Trump's threats to build a wall along the whole border and deport millions of illegal immigrants have not made them abandon their harrowing journeys and hopes of a better life in the north.

But for some like Juan Alberto Lopez, the prospect of living in a country they believe will become more hostile to people like them no longer holds enough appeal to make the risky crossing across the desolate Arizona borderland.

"Now everything's changed," said the despondent Lopez, 25, as he sat staring blankly at the ground in outside one migrant center, under a cobalt sky.

Lopez hails from the southern state of Chiapas, Mexico's poorest, and lived for two years in Arizona and Utah working in construction before being deported in January. Under one of Trump's proposals, he would face a two-year federal prison sentence for returning after deportation.

He had decided to go back to the United States when Democratic candidate Hillary Clinton was projected to win the election. Now, he plans to seek work in Nogales instead, or go home.

"They're going to detain all the migrants, and if it's like that, it's better to stay here with your own people, be happy, and just endure it," he added, echoing the sentiments of a third of more than a dozen migrants interviewed by Reuters in Nogales following Trump's victory.

In running for president, Trump promised to deport millions of illegal immigrants as well as build a wall along the border to stop others entering the United States, and make Mexico pay for it.

His uncompromising stance helped drive a rush over the U.S. border as some migrants calculated it was better to cross over before the election in case Trump won. That could continue in coming months even as some like Lopez decide they no longer want to live in the United States.

During fiscal year 2016, which ended in September, the number of people detained along the U.S.-Mexico border surpassed 408,000, a 23 percent jump from last year, although it was less than in 2014, official U.S. data published last month showed.

"I really don't care about President Trump. I'm always going to cross regardless of any walls he wants," said Alexi Solano, 20, a migrant from El Salvador, whose wife and young son are already in Los Angeles.

"That doesn't matter to us. What we want is to be together with our families."

Mexico's deputy interior minister for migration, Humberto Roque Villanueva, said he expected that flow to peak in 2016 as Trump will ramp up already tough deportation policies applied by President Barack Obama.

"A certain radicalization of the North American immigration policy is coming," Roque Villanueva said.

THUGS AND SNAKES

In Nogales, a city of 230,000 dotted with factories of multinational firms like Motorola and B/E Aerospace, migrants say people smugglers typically charge $4,000 per person for a one-way ticket across the border.

As with long stretches of the 2,000-mile (3,200-km) border, a 25-foot-tall fence already exists along the international boundary here, built in 2011 and made up of thick rust-colored metal beams that follow the rocky terrain for miles to the west and east of the city.

Beyond the fence on the U.S. side, a parallel set of wooden posts are topped with cameras and sensors. In the distance, U.S. immigration vehicles slowly patrol the border.

Some 25 miles (40 km) to the east of town, the towering fence comes to an end and is replaced with a waist-high barrier that mainly serves to stop trucks plowing through the desert.

While some migrants trudge around the barricade, risking weather exposure on foot through rugged terrain menaced by drug cartel thugs and poisonous snakes, others opt to ride hidden in trucks that drive through official crossings, a route made possible, several said, by bribes.

Maria Engracia Robles, a Roman Catholic nun who runs El Comedor center for deportees and migrants within sight of the border fence in Nogales, thinks Trump's victory will likely bring more hardship and worries about the challenges that mass deportations would bring.

"More anguish, tears, laments, and lots of people in Mexico without work, without anything to do and no place to go," said Robles, whose center provides free meals, clothes and basic medical care.

Braced against the dry wind, dozens of hungry migrants line up around El Comedor's entrance for breakfast each morning. On Thursday, two men just inside the shelter could be overheard on mobile phones asking for a coyote, or human trafficker, to attempt another crossing.

"Here there is no work, and salaries are terrible," said Robles.

The U.S.-Mexico border is home to the largest per capita wage differential of any land border on the planet, with average U.S. wages about five times higher than Mexican wages.

Further south, in Central America, incomes are even lower, and crime worse, fueling a surge of migration in recent years. More Central American migrants were apprehended on the U.S. southern border than Mexicans this year.

Jose Flores, 19, a Honduran migrant who set out for the United States three months ago, ticked off the perils posed by violent gangs and dismal job prospects in his home country.

"I imagine it's going to get a lot harder to cross," he said. "But what hasn't changed is we're looking for a better life."

(This story has been refiled to fix typo in 20th paragraph)

(Additional reporting by Gabriel Stargardter; Editing by Frank Jack Daniel and Kieran Murray)