Wow, I think this *really* depends on where you live. Around here (Seattle Eastside area in particular), if someone sees you on a bike during rush hour they assume you're commuting by choice, and if you're really spandexed out on a nice bike they assume you're on a training ride. Of course, they assume you're doing it to save the environment most likely. Show up to work on a bike and you mostly hear people say they wish they were in good enough shape to do the same.