Most forgo sleep for weeks to dance in the country that gave birth to the tango. Some stay for months, neglecting businesses and relatives back home, helped by a weak Argentine peso that makes food and lodging cheap by world standards. Judging by the Americans at Club Gricel, both men and women, most are divorced and over 50.
"Once you start coming, you have to come again, and you can't stop thinking about coming," said Anne Foreman, a real estate agent from Albany, Calif., who was spending three months in Buenos Aires on her third visit in three years. "I've dropped almost everything to be here. This dance has taken over my life."
Buenos Aires is clearly "the Mecca of tango." On the floor with Leon were dancers from Japan, Korea and Hong Kong, as well as other Americans, many of them from the San Francisco Bay area, home, they said, to the biggest tango scene in the United States.
Roughly a third of all of Argentina's tourists come to see and perhaps dance the tango, said Guillermo Alio, a former government official who now owns a tango-themed art shop in the city's historic La Boca neighborhood.
About 1.78 million tourists entered Argentina through its main Ezeiza airport last year. They pumped about $3.25 billion into the country's economy, about a 30 percent jump from the previous year.
There are tango tours for everyone, from non-dancers who just want to visit a club and watch to the enthusiast who wants to dance till dawn. The truly hardcore come on their own, however.
The boom has revitalized La Boca, the birthplace of tango, where dancers and vendors now fill the colorful streets every weekend.
"They are drawn to the party of blood and love that is Buenos Aires," Alio said.
Tango's in-your-face sensuality is clearly an attraction.
A typical dance, done right, starts with the woman wrapping her left arm tightly around her partner's shoulder and the pair fusing limbs and torsos. Their faces often touch, and their legs intertwine with the ebb and flow of the music.
"It's three minutes of romance with a stranger," said Ana Rossell, a Newport Beach, Calif., fashion designer who danced for almost three weeks in March in Buenos Aires. "The beautiful thing is, `I don't know you, and you don't know me, but as soon as we dance, it's like I've known you forever.' "
Several women said the macho ritual of tango, where sharply dressed men are the uncontested bosses of the milongas, or dance clubs, intrigued them.
The ritual allows only men to initiate dances and only by shooting glances at women from across the dance floor. Women are expected to dress in silky skirts slit to expose maximum leg.
"I go to milongas where I literally feel like a piece of meat," Foreman said as she watched the nightly ritual on Club Gricel's dance floor. But that feeling doesn't discourage her. "Look at these guys. They're kings in here," she said.
Whatever the attraction, the experience transforms many. Nine-to-five jobs back home feel worlds away. The milonga becomes the only thing that matters.
Back in California, Leon is a divorced father of two grown children who sells insurance. If he's lucky, he gets a chance to visit a tango club in the Bay Area, most of which close at 1 a.m.
In Buenos Aires, he's a tango vampire. Dressed entirely in black, he hops from milonga to milonga and dances until sunrise, sleeping only until the afternoon milongas begin. He seduces women like his Brazilian partner at Club Gricel and persuades them to prolong their vacations so that they can dance with him.
"You come here and dive into this stuff," Leon said. "It's like mainlining for drug users."
Some people, such as longtime Oakland, Calif., resident Deby Novitz, can't settle for a few weeks a year.
In December 2004, the 52-year-old technology consultant sold her house in California and moved to Buenos Aires to dance full time. She picked up an affordable three-bedroom apartment in the city's ritzy Palermo neighborhood and has turned it into a guesthouse for visiting dancers. It's often booked two months in advance.
At the milongas, the short-haired blond woman is a coil of sensuality, wrapping her legs around her partner's body while focusing on every push of his chest.
"I was coming here so often that my friends would never know if I was in California or Buenos Aires," she said. "And I started to ask myself, `You work 90 million hours a week, for what?' In the States, there was just something missing. I've found that something here."
Readers interested in tango tours to Argentina may be referred to the following:
For tango tours: Tango With Judy: www.tangowithjudy.com
Tanguera Tours (specializing in female travelers):
To reach Deby Novitz's tango guesthouse: www.lavidacondeby.com
To read more about the tango life: "Kiss and Tango: Looking for Love in Buenos Aires" by Marina Palmer. The memoir of a former New York advertising executive who moved to Buenos Aires to become a full-time tango dancer.