05/26/2008 at 01:00 AM EDT
The May 10 wrap party at Miami hot spot Nikki Coconut Grove celebrated the end of one union—the cast and crew working on Marley & Me's
Miami shoot—and the beginning of another. Jennifer Aniston
and John Mayer arrived hand-in-hand (Jennifer costars with Owen Wilson
in the film based on the bestselling book). At the party, a relaxed Jennifer, 39, introduced John, 30, to colleagues. "They were acting very much like a couple," says a source. "At one point, John hopped up on a table and took pictures." The pair also danced to '80s tunes, and later John fed her strawberries. Then, "they did a little kissing at the bar," says an onlooker. "It was really cute!"
The couple's PDA thrust them back into the spotlight, two weeks after they first raised eyebrows with a romantic weekend together in Miami. But their subsequent time spent apart—she continued filming; he worked in New York—fueled speculation that they had split. Not so: The singer has had a standing reservation at Jennifer's Miami hotel for the past several weeks and has spent "quite a bit" of time there, says a source. After spending more time with Jennifer last weekend (then heading off to Orlando May 13, where he played a private corporate concert while she snapped pictures backstage), John is already getting serious about her. "He's been throwing around the term 'love' already," says a pal. "He's fallen hard for Jen. He's pretty enamored."
So is Jennifer (who next travels to Philadelphia for more Marley
filming). But for now she's content to take a wait-and-see approach to the relationship. "The thought is, as long as she knows this is just a good time, everything's okay," says a Jennifer source. "And that's just what this is."