But getting there from his home in Las Manos, has proved much harder than expected. Vallecillo, wife Sandra and 4-year-old daughter Brittany have endured a fruitless wait for visas, spent all their money on food and transportation, and escaped a police raid in which hundreds of migrants were arrested and hidden out in the countryside.
Still, he remains determined to make it to Monterrey one way or another. The family is a prime example of how Mexico's crackdown on migration is not cutting off the flow of Central Americans, but rather forcing migrants into the shadows and greater danger, despite government assurances that the central thrust of its policy is to protect them.
For months, Central Americans have banded together in caravans and employed a 'safety in numbers' strategy, although efforts to discourage the large groups now have migrants wandering woods, swamps and rail lines in small bands of one or two dozen, exposed to the elements and also at greater risk of being preyed upon by criminals.
Vallecillo set out with the equivalent of 13,000 Mexican pesos ($680) in savings from Honduras. He'd heard that Mexico was handing out visas to migrants, and decided it was time to go to the factory job.
But hope turned to disillusionment when he found that Mexico wasn't handing out humanitarian visas at the border anymore, and the work visas it offered allow migrants to work only in poor southern states like Chiapas and Oaxaca where pay is low. The slow pace of visa processing has angered migrants.
After 27 days waiting for the visa that immigration officials promised but endlessly put off, Vallecillo and his family had enough. They joined the caravan of around 3,000 people that was passing through southern Mexico and then fled Monday's raid that broke the group up, hiding in a church and spending that night in the woods. By Wednesday they were sleeping under the stars next to some railroad tracks after local authorities in Arriaga, Chiapas, ran them out of the city park.
"They didn't want to see migrants there," Vallecillo said. "Once you run out of money, and you can't bathe or change clothes, people start looking at you differently, like the classic stereotype of a migrant."
His daughter has taken to eating seed pods from the ground. The family is now looking at hopping aboard a freight train for the rest of the trip, because they no longer have a dime. A man of calm demeanor, Vallecillo's resentment is nonetheless palpable. He said he has always worked, tries to keep clean and doesn't like being looked at as a transient person.
"Why did they have to deceive us?" Vallecillo asked. "If they weren't going to give us visas, why did they make us wait? At least they could have gotten out of the way and let us go through. We'd be in Monterrey by now, with a decent life."
President Andrés Manuel López Obrador's promises of a new, more humane approach to migration seem to be melting — under U.S. pressure — into the old, deportation-oriented policies of his predecessor, Enrique Peña Nieto, who launched a crackdown in 2014 that included police raids on the train line that Vallecillo now hopes to catch north. Many migrants fear raids on the train may start again.
Jorge Valladares, 35, and four friends from El Progreso, Honduras, have been walking and hopping freight trains for a week, avoiding the highways where numerous immigration checkpoints have sprung up. They are determined to reach the United States; but travelling on the trains they have had to develop a safety protocol of waking each other up whenever one dozes off, to ensure that nobody falls off.
"We are going to take the train, walk through woods, over mountains, but God willing, we are going to make it," Valladares said. Mexico has deported thousands of migrants in recent months and also issued more than 15,000 humanitarian visas, but officials say they are now being more selective about who gets them. Those detained in the raid this week were said to have refused to register for the regional visa that lets migrants stay in southern Mexico.
The migrants sometimes face the same dangers they were fleeing in Central America. One Honduran migrant said there are members of the Mara Salvatrucha street gang in the shelter where hundreds of migrants are waiting for visas in the Chiapas town of Mapastepec.
The man, who got a job as a night security guard in town, still lives at the shelter but is afraid to fall asleep because the Maras know he filed a complaint with police and have threatened to kill him. "It's when you're asleep that they can kill you," said the man, who did not want to give his name for fear of reprisals.
Officials commonly use the term "rescuing" to describe detentions of migrants, and some do end up in dangerous situations in need of help, such as when they're trafficked in hot, overcrowded tractor-trailers.
On Wednesday federal police and immigration agents picked up two Guatemalan couples and their two babies from the side of a highway in Oaxaca as temperatures soared near 100 degrees Fahrenheit (40 degrees Celsius). The migrants were so exhausted from the heat they didn't even try to run, which might have been impossible with the babies, anyhow.
But many feel they wouldn't be taking the kind of risks they're taking now if not for the raids and other measures. Dennis Javier Cortes, 21, walked with his wife and a couple dozen other Hondurans for 13 days, following the rail tracks to avoid detection and possible deportation. His feet, clad in open-toed sandals were battered and black with grime, with a half-inch-long gash on one toe.
"We drank water from ditches, from the swamps we passed. There was a crocodile in one swamp," Cortes said. Because they are in a mango-growing region, their main food supply on the trek has been fallen mangos.
He and his wife had already been through far worse: In February a gang in Arriaga dragged the couple into the woods and held a knife to Cortes' throat as they took turns gang-raping his wife, he said.
While that specific incident can't be directly tied to Mexico's crackdown, most migrants say they found safety in the large numbers of the caravans. Many now see caravans as becoming a thing of the past after the raids and the fear they instilled.
In social-media chat groups used to organize the exoduses, one person in El Salvador wrote this week: "you'd better forget the idea of travelling in caravans." One immigrant who had been deported back to El Salvador wrote that "they (the Mexicans) don't want any foreigners, much less in caravans."
"I was going to leave on the 30th but my brother who went in the (caravan) on the 10th was deported yesterday," said another anonymous chat participant. "They are blocking highways ... nobody is safe."
Others feel they have been stripped of their dignity by Mexico's migratory policies. Truckers, warned by the government they could face fines, no longer stop to offer rides, and immigration officials charged with handling visas are said to have become surly and cold in dealing with migrants.
Cortes and his wife filed a criminal complaint about the rape, something that should have gotten them automatic visas in Mexico as crime victims. But Cortes said immigration agents ripped up the documents during Monday's raid, which they narrowly escaped.
Associated Press writer Marcos Alemán in San Salvador, El Salvador, contributed to this report.