Ever heard the term “idiomatic expression”?
I asked exactly this question of some native speakers in Mexico a few years back.
Their answer was, it’s perfectly OK to say,
“Me da <algo>…por favor”.
The “Usted” is of course implied at the beginning.
Do I dare ask what a guiri is ?
Thanks for all the help, everyone. I guess what I really wanted was some kind of “verbal padding” to help me sound like a better speaker of the language, but I guess that’s not always needed.
(Guiri=not too polite word for “tourist”, I believe, although oddly I think it literally means “policeman”. Not too sure what the connection is.)
Spaniard version of “gringo”.
I know. And they have fun listening to you guys, including calling you “Sudacos”. 
The point in all those sentences listed in the original post is that they use either usted or the subjective, both of which are structures that do not exist in English per se. Spanish verbs have special forms both for polite address and for the subjunctive, whereas in English you mark those by adding extra words.
If you said “me traes”, that is impolite; you could say it to your brother but you wouldn’t normally say it to a waiter. If you say “me trae”, it’s perfectly polite. The me trae version translates as “may I have a bottle of water?”, me traes would be “hey dude bring me a bottle of water”
Spanish from Spain here.
Sudacas, not sudacos 
And in these times of political correctness it’s come to be considered a word to be avoided, but actually most people just use it as a shorthand version of sudamericano.
And guiri is a word that comes from the time of Nappy’s invasions. It was initially used to mean those who hailed the invaders as “liberators from the tiranny of monarchy”, moved fast to mean “collaborators”. Hence the first police connection.
During the Carlista wars, the Carlistas referred to the government as guiris (i.e., accused them of being sold to the newfangled ideas from France - police connection number two) and the guiris called the Carlistas carcas (short for “carcamal”, meaning old fashioned). Nowadays carca means “old fashioned” or “politically right wing + religious”, depending on context; guiri just means “foreigner with a lighter skin than me” You don’t call sudacas, chinos, moros or negros guiris.
Hence “gringo”.
And I knew “sudacas”. That’s what I get for not speaking a language for 10 years. :smack:
Actually, one of the most beautiful thing about Spanish is how expressive, flexible, flowery - and loaded with swearwords - it is. Maybe it’s an inheritance from the Moors, but no one but arabs can swear as poetically as a Spaniard.
Really? People frowned on “quisiera”? It’s possible it’s more used in Latin America (which in a lot of respects tends to preserve older Spanish usages.) That surprises me, though. The general principle that overly polite phrases can (oddly) sound extremely rude is right on target, anyway. It’d come across as creepy and weird if a man, on first acquaintance with a woman, got down on his knees and kissed her hand, too.
You can’t always translate everything literally. English politeness don’t translate well into Spanish. Actually you can politely request somebody do something in Spanish without ever using the words “por favor”, intonation and wording can do the same job, or better. “Tráigame una cerveza” can sound rude or polite depending on intonation alone.
Although any two Spanish-speakers from anywhere will understand each other, wording of the same phrase may vary (and still convey the same meaning).
And yes, everybody speaks Spanish funny and have an accent, but us. 