I never tried this at the mall, but I've been invited into the female bathroom of nearly every bar I frequent. Here's how I do it.
"While you're in there, let me know if they've got a couch or not."
There are a million variations you can use, make it situational. It works either in-set, or on the way to the restroom when passing a girl who has seen you that night, but not talked with you yet. I don't think there is a bigger DHV than when a girl from a set you are with walks in on you and 2 girls she doesn't know doing a photo shoot on the women's couch
