NOGALES, Mexico – At a shelter overflowing with migrants airing their blistered feet, Francisco Ramirez nursed muscles sore from trekking through the desert – a trip that failed when his wife did not have the strength to go on.

He said the couple would rest for a few days, then try again, a plan echoed by dozens reclining on rickety bunk beds and carpets tossed on the floor after risking violent bandits and the harsh desert in unsuccessful attempts to get into the United States.

The shelter’s manager, Francisco Loureiro, said he has not seen such a rush of migrants since 1986, when the United States allowed 2.6 million illegal residents to get American citizenship.

This time, the draw is a bill before the U.S. Senate that could legalize some of the 11 million people now illegally in the United States while tightening border security. Migrants are hurrying to cross over in time to qualify for a possible guest-worker program – before the journey becomes even harder.

“Every time there is talk in the north of legalizing migrants, people get their hopes up, but they don’t realize how hard it will be to cross,” Loureiro said.

South-central Arizona is the busiest migrant-smuggling area, and detentions by the U.S. Border Patrol there are up more than 26 percent this fiscal year – 105,803 since Oct. 1, compared with 78,024 for the same period a year ago. Along the entire border, arrests are up 9 percent.

Maria Valencia, a spokeswoman for U.S. Customs and Border Protection, said the rise in detentions did not necessarily mean more people were crossing. She attributed at least some of the additional detentions to an increase in the number of Border Patrol agents.

“We’ve sent more technology and agents there, and I think that’s had an impact,” she said.