"People are going to get sick of seeing her face everywhere," jokes manager Stephanie Nese. "Melonie is a trouper. She's always in a good mood because she's worked for about two years straight and this is a celebration."

After all the daily meet-and-greets, the refreshingly low-maintenance, somewhat salty-tongued starlet still finds time to party, catching a late-night concert by punk priestess Patti Smith, whom she describes, reverently, as "such a badass." Getting to bed by 2 a.m. is an early night.

"Melonie has a battery inside her that could drive a locomotive," says Black, her "Be Kind" costar.

Fleming, "Hamlet 2's" director, enlarged the part when Diaz signed on. "I didn't want somebody doing a caricature of a Latina. I felt she deserved more. Some people have the ability to be interesting on camera. Every time you look at Melonie, you see something else. The shape of her face and the way she holds her head is very photogenic. She's dazzlingly pretty but not in an unapproachable model way."

Proud to be 'Nuyorican'

Gondry, who cast her in his New Jersey-based film because he needed "a strong actress, not a typical star," sees Diaz as an original. "She has a great look, but it is very real. You can believe that she's coming from that place."

The second daughter of first-generation Puerto Ricans raised on the Lower East Side of New York City, Diaz proudly calls herself a "Nuyorican." Her father, Carlos, worked for an advertising agency and is now retired and living in Puerto Rico. Her mother, Beatriz, is a clerk at an AIDS hospital.

"They are polar opposites," she says of her parents, who split when she was 7.

She took after her outgoing, "people magnet" father, entertaining neighbors by reenacting Janet Jackson and TLC music videos with her older sister, Mercedes. At 12, Diaz began to explore the sensitive side she sees in her mother, appearing in student plays in a city arts center. She became an old movie fan, soaking up the great performances of actresses such as Bette Davis.

"I love her in 'All About Eve,' " Diaz says. "She's a total bitch."

NYU film student

Upon graduation from the Professional Performing Arts high school, Diaz enrolled in a filmmaking program at New York University. "I don't know how I got in with 860 on my SATs," she admits, adding sassily: "Affirmative action, baby."

She has a year and a half left to complete her degree. "I also failed some classes, like the history of Western art, because I couldn't remember dates," she admits.

Her approach to her craft is more organic than scholarly. "I am not a Method actor. I don't know how to build a character," Diaz says at a late-night "Hamlet 2" party, a glass of white wine in one hand, a tumbler of ice water sensibly parked nearby on the bar.

"It's a little conceited to say you are natural, but that's what people have said about my performances," she notes, watching her cast mates dance to the thump of Timbaland and Rihanna. "I can only justify it by saying I am playing a part of myself."

And with that, this year's Queen of Sundance hits the dance floor, just another New York City girl hanging out with her friends.

david.keeps@latimes.com