Across the country, tens of thousands of undocumented immigrants who arrived in the U.S. as children had marked on their calendar the date Feb. 18 – the day that the Obama administration had set for when it would begin accepting applications for an expanded deportation deferral that President Barack Obama announced in December as part of an executive order on immigration.

The deportation protection would last three years, and along with it for those who qualified, would also come eligibility to work here legally, to get a Social Security number, to get a driver's license and even to obtain some government assistance.

Nancy Perez, a 38-year-old who was brought from Mexico to the United States illegally when she was 13 and who qualifies for the expansion, told Fox News Latino last week that she was anticipating a better life.

“I’ve lived here 25 years, most of my life,” Perez said. “I love my native country, but this is the country where I really grew up, where I went to school, where my children were born.”

I’ve lived here 25 years, most of my life. I love my native country, but this is the country where I really grew up, where I went to school, where my children were born.

— Nancy Perez

But just hours before the day that would have marked a first step out of the shadows for her and others eligible for the program, a federal district judge in South Texas temporarily blocked President Barack Obama's executive action on immigration.

On Tuesday, immigration advocacy groups and community leaders, who had been scrambling to encourage immigrants to apply and help them complete their paperwork, expressed hope that the Fifth Court of Appeals would reverse the ruling. They also urged immigrants not to abandon plans to apply.

"It's extremely important for the community to understand from a legal perspective, it is on solid legal footing and actually the larger number of people who come forward to apply, the more likely we can protect the expansion," said Marielena Hincapie, executive director of the National Immigration Law Center.

The immigrants struggled to balance optimism against disappointment.

"We feel powerless but not defeated, sure that it will all work out," 46-year-old Claudia Ramón, a native of Colombia, said at a rally in Houston, one of dozens of demonstrations nationwide at which immigrants and advocates vowed to continue with preparations under Obama's proposed programs.

In contrast, proponents of strict immigration enforcement are lauding the judge's injunction.

Roy Beck of NumbersUSA said in a statement: “Struggling American families can find hope in the judge's ruling which at least temporarily halts the issuance of work permits in March that would have begun allowing millions of illegal foreign workers to compete directly with American workers for new job openings."

In 2012 Obama announced an initiative to defer deportations for undocumented immigrants who had been brought here as children, were under 31 years old, enrolled in school or had a high school diploma.

Perez missed the cut by four years.

Obama’s December executive order could benefit up to 5 million people. That includes some 300,000 who came as minors and did not qualify before, but do now that the maximum age limit was lifted, as well as millions of other undocumented immigrants who have children who are U.S. citizens or legal permanent residents.

The latter group were to begin applying for deportation relief in late Spring.

Perez, who lives in Arizona, would qualify under both categories since she came to the U.S. before the age of 16, has never been in trouble with the law, and is the mother of U.S.-born children.

She gathered all her documents, went over every part of her application with the help of Living United For Change in Arizona, or LUCHA, and got together her $465 fee.

“You feel relief knowing you can get DACA,” Perez said before the judge's injunction, using the acronym for the 2012 initiative, Deferred Action for Childhood Arrivals.

She felt that "to finally be able to have permission to work, and to get a driver’s license – I can start my life.”

In New Jersey, Giancarlo Tello knows first-hand what that feels like.

A 25-year-old political science student at Rutgers who was brought here from Peru when he was 6, Tello qualified for DACA in 2012. That enabled him to get a Social Security number, a driver’s license and to qualify for a two-year, $22,000 scholarship.

Tello – who like so many Americans grew up reciting the Pledge of Alliance every day in school and trading Pokemon cards with friends – hid his undocumented status from his peers for a long time.

When classmates got old enough to get driver’s licenses and cars, they questioned why he hadn’t.

He made excuses, said he couldn’t afford a car, so why bother.

Unable to drive, Tello would stay on campus from the time his father dropped him off at the crack of dawn, on his way to work, until about 11 p.m. every day.

“DACA helped me have a normal life,” Tello, who is active in efforts to improve opportunities for young undocumented immigrants in New Jersey, told FNL. “I had to stay on campus all day, even though I had one or two classes, because I had no way to get back home,” he said.

Education is also part of the plan for Perez, who had to drop out of school as a teen to help her mother financially, and then became a mother herself.

She has been taking classes to earn credits and has only one exam left to take before she can receive her GED.

“I always wanted to finish high school,” she said.

Eventually, she said, she would like to have legal permanent residence here and then become a U.S. citizen.

“But you have to start somewhere,” Perez said.

Another longtime immigrant in the U.S., Sabine Durden, 57, welcomed the judge's ruling putting a halt to Obama's immigration plans.

Durden came here from Germany more than two decades ago legally as the wife of an American citizen. For many years, the Moreno Valley, California, resident questioned the U.S. government's policies on immigration, but after her 30-year-old son was struck and killed by a driver who was in the country illegally and who had a prior criminal record, she became an activist.

"It didn't have to happen," she told the Associated Press.

While she voted for Obama, Durden said she was disappointed by his recent programs on immigration.

"I am happy that finally somebody put a foot down and said we can't just do whatever we want, not even the president," she said.

The Associated Press contributed to this report.