At the very mininum one of the three people in front of you will begin their order with "Can I get....." or "I'll take...." (as opposed to "I'd Like...." or "Please may I have......")
It's likely my Americanism shining thru but I really don't understand the problem Brits are supposedly having with this (at least in 21st century). Languages surely evolve, we no longer
taketh or
seeketh, and
"Can I get" seems like a perfectly acceptable way of speaking in casual situation. Of course I use it often in coffee shops, bars, stores, etc, but when I am at say a restaurant or in a setting where more formal/polite use of language is called for, I would never, ever say
"Can I get..." but always
"May I have",
"I'd like". I also see other people, i.e. Americans, in similar situations doing much the same, actually
"I'd like" is fairly common even in everyday situations. Of course there are simpletons everywhere but as a general rule, that's my experience anyhow.
Although it may well be, that in the USofA, we hardly ever have time/chance for more formal settings in everyday lives, we've never any time, nor cultural history to speak of, nor a Queen to bow to, so
"Can I get..." it is - most of the time.