I started this thread, and I haven't been following it lately, but I just wanted to comment on the other posts. I don't mind if my neighbors are out on their balconies when we are, and I don't really care what they do, as long as they aren't loud and disruptive. If someone comes out with a boombox or is drinking and gets loud, they become an annoyance to other passengers.
As far as having sex on the balcony, nightime or while your neighbors are at dinner is a much better choice than right after lunch. You can't expect your neighbors to stay inside because you are "using" the balcony, and it would be embarassing to be doing it with your neighbors only a few feet away on their balcony, so just pick a time when your neighbors are unlikely to be out.