Mister Fella

I was inhabiting the steps of the metro station yesterday, waiting for a friend, when along came a different sort of friend. One with lots of fur and a big appetite. He came right up and tried to slobber my face (I objected). I've seriously considered how I might take one of these pups home with me. Some are small enough to fit into my satchel, but I don't like those ones. Some are big and oafish, just the way I like them, but those ones would be too noticeable. I can picture the confrontation with my (wicked) land lady: ¿¿Qué?? No entiendo que estás diciendo. No hablo inglés. ….. Pero, ¿perro? ¿Cómo? No es. No sé. Eres loca.

Well, anyways. The point is: My metro friend--we'll call him Lucca--hung around the station for a while. I could tell that he knew he wasn't supposed to be inside because he was sort of cowering about, the way dogs do when they know they're going to get booted off the bed or something. This woman came along, a Good Citizen sort of woman, and began coaxing him to follow her out of the station. She held her hand out and said, "Ven!" (Come!) And then, when he didn't follow, "Venga!" (Come!) I found this interesting only because "Venga" is the more polite (Usted) way of saying "Come." I do my best to use the Ud.form in the appropriate situations. But, honestly, I don't really get it. There are people I talk to whom I refer to as tú, Ud., and tú again, all in the course of one conversation. I worry that they think I am better than them if I refer to them as tú, and they respond by referring to me as Ud. So then I try out Ud., but that's awkward because I falter over Ud. forms more than the tú. So then I default back to tú, and to hell with deference..
So...this woman really did my head in. Am I supposed to address these street dogs using Ud.? What in the world? And the janitors at work? They're tús? ... Falta algo. I don't understand.