A source told E! News that the pretty pair are expected to tie the knot in early September at Lake Como.
An eyewitness overheard Teigen and one of her girlfriends chatting and drinking Moët & Belvedere and talking about wedding plans at Wall at W South Beach on Friday night.
One of the model's friends apparently said, "Of course I am going to the wedding," with our source adding that Teigen chose Lake Como because "that's where they fell in love."
Source also noted that guests would be staying at Lake Como for about four or five days for the wedding.
Teigen and Legend became engaged in Dec. 2011 when the Grammy-winning singer popped the question over the holidays. They've been together since 2007.
"It was very sweet," the Sports Illustrated stunner told E! News at the Guys' Choice Awards. "I actually read it online on E! and I forwarded it to my friend Melissa, and I was like 'Look what he said!' I mean, it's so cute. I know he's John, but you still want to forward it along and be like 'Look at my boyfriend! He's adorable.' It was very sweet."