Well, at this point, with wireless technology so new, you are pretty much at the mercy of the people around you. I would say that your best solution would therefore be to do your browsing "off" of your actual machine.

Or websites could get a clue about security and self-sign their certificates...?

Maybe it's just me but the "well only access <insert website /> from your home where there's a slightly less chance your traffic is being monitored" doesn't seem like a good excuse :)