Yeah, maybe you're right. This is not a question I come across very often, because I only go to dances where I know everybody in the States. The women who ask me normally do know when I want to dance. When the Bahia Blanca comes on, normally I am looking at that particular dance partner looking back at me. Men may not be very observant, but the point is that it is their job to be observant in the milonga. They watch who dances well, and they do their best to dance with those. I don't necessarily use that criterion, but I am always watching. One might say that the male of the species is not necessarily the more observant or the best at dancing. In that case, the man has no business at the dances at all. There are traditions that go along with every dance. I really didn't consider where I was before I answered this post the first time. My body may be here, but my head is almost always somewhere else. I have to wake up before I write any more.
So, here is a better answer. Some women are good at being rejected, some are not. Some men are observant, some are not. Some women can tell when I want to dance, some cannot. There are just some things that are different with different dances, different groups of people. Women have even asked me to dance when I had a plate full of food. The tradition where I am from and everywhere else I have ever been is that a gentleman simply does not turn down a lady at any time, except in the milonga. And that is not quite true because the lady does not ask in the milonga. The man asks. On the other hand, things change, even in the milongas in Buenos Aires. At certain milongas, ladies sometimes ask the men. They are mostly young people. Then again, this only applies to women who are strangers to me. I am always glad to accept an invitation to dance from the right partner. But the original question posted did not make any accomodation for that. Still, if I had to choose between women asking and men asking, I prefer to ask, not to be asked. There is no easy answer to this question, but I still prefer to ask. I also like to go with friends who have partners. I can dance with their partners, and they can dance with mine.
Who knows, SK, maybe we shall meet on some dance floor someday, and you can ask me to dance and I can ask you to dance, and we'll both be happy.