In general, beginning leaders invite, and beginning followers accept, dances with whomever to whatever music is playing.
(Mostly tango, vals and milonga usually come later.) Men tend to ask any woman who appears to be available, however, this can be risky and potentially ego-shattering.
Naive men are frequently rebuffed by experienced women who prefer to not dance with leaders with little experience, and men often have no idea why they were turned down.
They also have no clue about cabeceo, etiquette, tradition, and possibly even tandas and cortinas.
Women…the same. They gleefully accept invitations from anyone who asks, because their main goal is to gain experience, and in the process may become confused if their partner leads moves they do not understand.
Prolific dancing is valuable, has its place and time in our tango life, and is most productive when combined with group and private lessons, guided practice, attending milongas.
Learning, sharing, enjoying The Dance is where our tango life begins.
Polly's Tango Talk 