As far as I am concerned, they are not passing any message because you are involved in bitcoin, that's why it made sense to you. To the man on the street, with no business with the internet, that is just another big billboard that does not make any sense to him.

I have seen some bills around here and also banners in front of shops that deal with buying and selling of e-currency but they try to bring several items together in other to attract buyers such as PayPal, PerfectMoney, Payoneer and the likes. So, its nothing new at all and come to think of it, the banner might have been there even before you got involved but because you knew about it, that's why you noticed something is there.