while posters and cards for other venues aren't going to happen because that's advertising for the competition.
Cards or advertising for other events is fairly common at both tango and other social dances here. That is how I come to know, esp about upcoming live music milongas that I love to attend. I am not a social tango creature so word of mouth reach to me is limited. Neither am I on social media, which I thing is one of the worst thing that happened to humanity in context of socialization. For tango we have a well maintained calendar on its own dedicated website. Therefore unlike places where there is no regular updated calendar, it is easy to find what’s going on. When I am visiting, the locals will inform about milongas and practicas when asked or volunteer knowing you are a visitor.
That’s true. Elsewhere in the world, WhatsApp is used for everything including commerce, making payments, etc. Its messaging features are far better than other messaging apps. telegram comes and signal come close but people don’t use them as much.I get the impression that WhatsApp is a thing in Europe. In Canada and the U.S.A., it lags behind. (I have the app, but I've never actually exchanged messages on it, and I receive only spam.)