I always ask for the John. Never had any complaints yet.
Where are you from?
I can vouch for the fact that “washroom” is a Canadian thing. I was in Santa Cruz last year and asked for the location of the ‘washroom’… the waitress gave me a blank stare.
The really funny thing is that some people, when they ask me where the restroom is (I’m a librarian) will actually say, “Do you have a restroom on this floor?” as a sort of weird polite work-around. As if they were just, you know, curious. Maybe because they’re drawing a map or filling out a survey or something.
Well, if you want to ask where the restroom is, what’s wrong with ascertaining whether there is one in the first place?
My wife, who is American, learned her lesson after asking for the “restroom” in an English pub and had the piss taken out of her about why she needed a rest. For visitors to England who do not want to be so gauche as to say “toilet”, just ask for the Ladies/Gents (as appropriate). This doesn’t work in private homes, of course.
Restroom is my preferred euphemism - and I recognize it as such.
I have long been annoyed by young women here in the US who will openly announce, “I have to pee.” God, that’s gross and unnecessarily specific, yet women whom you’d think would be more refined freely use that line in all company. It’s childish. A man should be equally admonished for a similar announcement, but he’d trend towards the less childish “piss” and moreover he’d know it was rude - whereas it would not be uncommon for a virgin bride clad in white to proclaim how desperately she needs to pee. Ugh.
Virgin bride?
Whatever happened to the word for toilet/restroom/bathroom, “john”? Or “jane”?
“I need to take a leak…”
“I gotta visit the euphemism …”
“I have to see a man about a dog…”
Huh. I didn’t think they even made those anymore.
When out in a public place, I’ll usually ask, “Where’s the men’s room?”
In someone’s home, how I ask will vary. Bathroom, washroom, whatever. I wouldn’t ask for the “toilet,” because that’s the porcelain object and I’m asking about the room it’s in.
My go-to word is “Ladies.” In all my travels in Europe and the Americas, it’s never failed me.
“Pardon me, where’s the Ladies?” Has always worked and nary raised a brow.
Oh sure, it makes sense if you’re a woman. If you’re a guy it means something totally different. 
“Where the white women at?”
It is known in the U.S. but not universal. I think you would hear it mostly in the Midwest and mostly among older people.
The traditional version refers to a horse.
Well, it’s a public library. There’s one somewhere.
Well, after she had the piss taken out, she wouldn’t need to use the “restroom”, would she?
Personally, I always ask for the “facilities”. Never had anyone misunderstand me.
I’m Australian.
Ah, that explains it. Australia is famous for reverse snobbery.
I can see how it might look like that - to an American - but it’s not “reverse snobbery”. Nobody cares if you are genuinely of delicate sensibilities, and we’re perfectly respectful towards little old ladies and so on.
What we dislike is affectation. What, you’re too delicate to say the word “toilet”? Grow up, fer chrissakes. We all use them, pretending they don’t exist is acceptable for little old ladies, but if you’re not a little old lady who’s lived a very sheltered life, don’t talk like one.
I’ve always used “men’s room,” as in “Where is the men’s room?” In America, which is where I live, I’ve never been misunderstood. The men’s room is that particular room set aside for the use of men, just as the “ladies room” is that particular room set aside for the use of ladies, or women, if you prefer. Both place refer to a room where the designated sex may retire to perform one or more of multiple tasks, including both urination and/or defecation. I’ve never been directed to a “men’s room” that did not contain a “toilet” and, usually, though not always, a “urinal.” I can’t speak to what may or may not be found in a “ladies room.”