I've ****ed a girl in a not-well-secluded clothing store dressing room, with just a little curtain in the doorway, not a door.
My ex told me that some of the hottest sex she'd ever had was getting ****ed against the wall of a church (I think she said it was the only time she'd done anal, too.)
I've done it in an elementary school soccer field at nighttime, and in a couple secluded spots around my high school.
Movie theaters and bathrooms (especially bar and club bathrooms) are legendary sex spots (I don't remember if I've ever had full sex in a theater, but I'm sure you could find an empty one and sit in the back row.) Neither of these sounds very appealing, though, on account of the stickiness you might encounter everywhere.
Sex in public places is a huge turn-on for many people, including girls.
This IS a freakin porno and you CAN just **** wherever the heck you want. If the cops catch you, it's most likely that they'd just tell you to leave, but it's possible they'd call your parents and even less likely that they'd ticket you. Anyone but the cops catches you? Laugh it off, and leave if they won't.