"I would make out in the park! That's the thing I would most enjoy doing in New York, and it's something I'll never do," Portman told the mag.
She'd also like to have loud, public conversations with her friends about personal things.
"Even if no one is paying attention -- and most of the time, no one cares -- you never know who is at the next table."
The typically tight-lipped actress opens up about what her soon-to-be hubby, dancer Benjamin Millepied, must have done to win her heart: be her best friend.
"I look for all the same things (in a mate) I would in a friend. Obviously, you need the sexual attraction too, so it's like your best friend who you are also really attracted to," Portman says, adding that she hopes to keep her relationship with Millepied as private as possible.
"This is the most private of private experiences," Portman told InStyle. "But I am completely awed by the whole process we are living through. I cannot express how lucky I feel."
Her new movie, "No Strings Attached" with Ashton Kutcher, explores whether friends can sleep together and still be friends. Portman believes it's possible, but it isn't for her.
"I certainly have friends who could deal with that and others who could not," she says. "It's something I've seen in high-achieving women -- they compartmentalize. You've got your work, your friends, your exercise, and your sex. (Grins.) You can tick off those boxes."
Pick up a copy of InStyle's February issue on sale this Friday, Jan. 14, and go to InStyle.com for more Portman.