But now, led by young people like Mr. Lujana, thousands are coming back. With violence down to a quarter of its peak, Ciudad Juárez, a perennial symbol of drug war devastation, is experiencing what many here describe as a boom.

New restaurants pop up weekly, a few with a hipster groove. Schools and homes in some neighborhoods are gradually filling again, while new nightclubs throb on weekends with wall-to-wall teenagers and 20-somethings who insist on reclaiming the freedom to work and play without being consumed by worry.

“It’s a different city,” said Mr. Lujana, 31, who moved back a few months ago. “The drug dealers have receded; it’s not cool anymore to be a narco.”

Juárez has often been a bellwether in Mexico, from the immigrants heading north along the first Mexican railroads in the 1880s through the growth of factories and free trade a century later. Then came the killing, a three-year spree starting in 2008, and now a reprieve that other violent areas still long for, as this gritty city trades paralysis and grief for stubborn hope, unresolved trauma and rapid reinvention.

Critics here fear that the changes are merely cosmetic, and there is still disagreement over what, exactly, has led to the drastic drop in violence. Some attribute it to an aggressive detention policy by the police; others say the worst killers have died or fled, or that the Sinaloa drug cartel has simply defeated its rivals, leaving a peace of sorts that could quickly be undone.

Whatever lesson Juárez holds for Mexico remains elusive, as Mexico’s struggle with lawlessness continues to evolve. The federal authorities are struggling for control in two Pacific states that are divided between vigilantes and gangs while, nationwide, prison breaks, grisly murders and record-high kidnappings still grab headlines.

Much of this city nonetheless looks and feels refreshed, a turnaround visible immediately upon arrival. Two years ago, Juárez billboards were sad affairs, old and fading as businesses closed or operated in the shadows to avoid extortion.

“Everyone had to stay hidden, like rats,” said Cristina Cunningham, president of the restaurant association here.

Now, bright new placards advertise dance studios, homes for sale and new restaurants on Boulevard Gomez Marin, where at least 15 eateries have recently opened. Posters promote events returning for the first time in years, like theater and the circus, and twice as many American tourists have come to Juárez this year compared with last year, according to the Chamber of Commerce.

The nights here, surprisingly for anyone who has visited since 2008, no longer resemble a war zone with a sunset curfew. There is traffic after dark. Drivers make eye contact, and a half-hour wait for a restaurant table at dinner has become one of the many signs of revival.

“You can walk in the street now,” said Jesus Rodriguez, 25, clearly amazed. “You have to be alert, but you can do it.”

That simple improvement lies at the root of the city’s cautious re-emergence — and its evolution in tastes and attitudes. On one recent evening at Mr. Rodriguez’s restaurant, La Toscana, which opened in January featuring a wide variety of pizzas and small plates mixing Italian and Mexican flavors, every table was full, mostly with what had been an endangered species here just a couple of years ago: young couples out on dates.

Mr. Rodriguez, slight and shy, wearing a black chef’s coat, said he returned to Juárez as soon as he could after moving to Guadalajara in 2006 for college and then staying away because of the violence. He found the money to open La Toscana through “family sacrifice,” he said, and took a chance with a new business because he and his friends were tired of putting off their aspirations.

“We were in standby mode for so long,” he said. “We were just looking for a little light.”

Mr. Lujana needed more convincing. He resisted when his friends pushed him to cross into Juárez from El Paso for drinks at a new club in early 2012. “I was still scared,” he said. “I kept thinking, no one’s going to steal my car? But then I saw my friends, and some of them had nicer cars than mine.”

He was already unhappy in El Paso. At the restaurant he co-owned, taxes were high, customers scant, and waiters often just didn’t show up. Many Texans, he said, seemed hostile toward anyone from Juárez.

“It was very depressing,” said Luis Rodriguez, 40, Mr. Lujana’s business partner. “We were creating jobs, paying taxes, but we weren’t treated very well.”

About a year ago, they started looking for space back on the Mexican side of the border, where rents were around 60 percent cheaper. They found a spot near some other restaurants that recently added dinner service after closing early for years, and re-created the Brazilian grill they shuttered in El Paso.

“I’m optimistic,” Mr. Lujana said during a typical lunch rush. “Before, my friends went to El Paso for fun. Now they come here.”

Many young people here say that is because Juárez has become more interesting. “The clubs are doing new things,” said Aime Tenorio, 19. “They have really good D.J.s, or Victoria’s Secret models. It’s so easy to open a bar here, so people are really loving it.”

Even many of those who have not returned full time slip back in. What had been considered crazy — an overnight trip to Juárez — is now, for many, a worthwhile adventure. Aura, one of the first clubs to open in the new boom, even offers a package deal every Thursday through Saturday, with bus service from El Paso, an open bar at the club, a hotel room, and a return trip across the border the following day for about $350. Another company, Alive, provides transportation to and from El Paso in a single evening.

“Business is good,” said Arturo Velarde, 26, a partner in Aura, which has a capacity of about 1,200 people. “It’s not like it was before, but hopefully it will be.”

A full recovery, though, may not be where Juárez is heading. Before the violence peaked, this was a wide-open city of endless work and new arrivals from all over Mexico. It was often called “the big sister that supports the rest of the family.” But experts say Juárez, where the population tripled from 1970 to 2000, reaching 1.2 million, may never match its prior growth. Tourism is half what it was in 2007. Business groups, school administrators and returning residents estimate that only about 10 percent of those who left have returned.

Alberto Ochoa-Zezzatti, a sociologist at the Autonomous University of Ciudad Juárez, recently published a report asserting that about 450,000 people fled the city from 2007 through 2011. The best Juárez could hope for, he said, based on migration patterns after natural disasters, was that a little more than 20 percent would come back.

And the city’s sense of itself is still shaky. The newer housing developments attracting returnees feature new playgrounds behind high walls. “We’re starting from zero,” said Ms. Cunningham, 50, whose family recently opened a club called Kaos. “This city has seen a lot of trauma, and we’re forever changed.”

Many say the ills of Juárez have only mutated, or receded from view. Criminal conviction rates are still abysmal. Extortion is still a problem, especially for businesses that have been paying for years, and many poor neighborhoods are still deadly.

Some see a bust around the corner. Ms. Cunningham said government officials have been too busy congratulating themselves to notice that there are too many new businesses for too few customers. “If they don’t do something for this city,” she said, “all of this is going to collapse.”

But for many here, hope is just beginning to surge. Mr. Lujana said most of his friends and relatives have recently come rushing back, many with new ideas and a determination to make Juárez more prosperous, responsible and fun.

On Halloween this year, crowds of young people — half from El Paso, half from Juárez — danced, drank and laughed at clubs with high-energy music and fake blood on the walls, as if mocking the violent past, hoping to render it harmless.

“Young people here, now, we want a different culture,” Mr. Lujana said. “We want a different life.”