She wouldn't go through with it.
Well the time when "J" pulled my cock out while we were at her place watching tv in the living room (she was living with those Lord of the Rings geeks) and started sucking, was really exciting. The fact that any of them could come out any second and catch us was a thrill. One of them did go into the kitchen from his garage-turned-dragon-slayer-dungeon, and we didn't hear him until the last second.
The time many years ago when I was beat off in the parking lot of Ihop by that girl Erin, was equally as hot. We also basically dry-humped on a different occasion on a bench in front of the capitol building too.
If it were for stupid obscenity laws and for her not feeling it, I would love to try fucking in public.