It is definitely true that most people don't care all that much about your hobbies and will at most ask about anything strange they observe just to make conversation. Continually advertising your aikido obsession (meant in a good way, of course
) will not make you well-loved any more than any other type of let's-talk-about-me conversation will. However, from experience, I think it is important not to go too far down this road. At some points in my life, I've ended up exchanging only a couple of words a week with other people because there was nothing I wanted to hear about from them, and I assumed they didn't particularly want to hear anything I had to say. That starts to affect you and your life after a while, and I think not for the better.
As a result of such considerations, I don't advertise my obsession with aikido, but I don't hide it either. If someone asks me where I am going with that pointy-looking bag, I'll tell them it's sports. If they ask what kind of sports, I'll tell them the name (which will usually require further explanation). In most cases, that is enough. In others, people become interested and may in fact be stimulated to try the art out for themselves. There are several friends and acquaintances of mine who I introduced to aikido that way, and I certainly don't regret not being secretive in their cases! Of course, it helps to make no claims super-stealth-ninja-sokesmanship to them (unless that really applies), because that is laid to rest pretty easily after stepping on the mat. . .
So I think forgetting about the whole deal may be safe. Give an answer if asked, but don't worry overly as few people really want to know much. Carrying a jo to work isn't exhibitionism if you don't intend it to be.