Hey Jen — Watch Out for John!

Love was definitely on the menu when Jennifer Aniston dined with musician John Mayer at Miami's Café Sambal on April 27. "They were looking into each other's eyes," an eyewitness tells OK!. "It was definitely a date!"

At one point during their meal, Jen, who giggled and smiled like a schoolgirl, discreetly took John's hand. "It looked like they were in love," says the onlooker.

The sexy dinner was the third time that Hollywood's golden girl, who is in town filming her next movie Marley & Me, paired up with the funnyman rocker in 48 hours!

"It's a very new thing," a source close to John tells OK!. "They're still in that 'getting to know each other' phase."

But the 39-year-old actress may want to be cautious about this potential beau. Friends of the 30-year-old Grammy-winner say he has a long track record for leaving women heartbroken. "Girls fall for him hard because he's charming," one friend tells OK!, "but he has a reputation for crushing the girls he's with."

Jessica Simpson and actresses Minka Kelly and Jennifer Love Hewitt are just a few women who have been wooed by John.

"He came on so strong at first," a pal of Jessica reveals to OK!. "He wanted to be with her every moment. When he wasn't physically with her, he was texting her — but all of a sudden, he got bored and stopped returning her calls."