If you're more confident than you can try right beside the road. You see a lot of pictures on the Net of girls doing this. I think if people see you being photographed naked by the side of the road, you're probably a lot less likely to get stopped. The other person validates what you're doing, but they still enjoy the view. On a similar note, try doing it from an overpass.
Rooftops offer a similar vantage point, but are a bit riskier.
Anyone who gets the idea, such as a cop, could get in the building and get up to you before you can be scarce. With a little attention you can watch for that though, and be inside hiding somewhere until you can get dressed and out. Glass elevators offer a similar distance, and make it easier to get away quick. Another way to keep out of reach is transportation. I like to show off from the back of a convertible, but I realize that's not for everyone.