This is quite an extensive and accurate  list  but, in real life, a  native speaker , especially a stranger (in the US at least)  would ask about the bathroom location within a very small range of  questions. For example: 

Excuse me , do you know where the restrooms are? 
                do you know if   there  is a restroom around here?
                do you know where the men's room is? 
                 is there a ladies room  around here? 

                can you tell me where the men's room  is?

The others would be used very rarely, if at all,  even between native speakers. (My opinion only)

I agree with Thomas. Most of those terms are very rarely used. And if they are, they're only used in jest. I very much doubt that anyone - native or not - would ever accost a stranger in the street asking for john/head(s)/latrine or any of the more vulgar variants suggested.

The exception, of course, is 'loo', which is the standard informal word which you can use in any situation in the UK -  'loo' is essential vocabulary for any visitor to these shores.

It's also worth pointing out that the convention of referring to a room with just a toilet in it as a 'bathroom' is confined to speakers of American English. For the rest of the English-speaking world, a bathroom has to have a bathtub or at least a shower in it to qualify as a bathroom. Outside of North America, we use bathrooms for bathing, and restrooms for ...resting, I suppose.

In GBE, we also refer to the room with the toilet in it as 'toilet', which is we're less coy about saying the word in polite company than AmE are.

In the United States, in an ordinary situation where you are asking strangers in public, by far the most common phrases would be "men's room," "women's" (or "ladies'") room, "restroom," and "bathroom."

"Men's room" and "women's room" would be common because that's the way they are most commonly designated in public. "Restroom" would also be common because, again, that's the way it often appears on signs. "Bathroom" would be the way you'd ask in someone's home.

There are a variety of euphemisms, idioms, and jokes, but if someone saw that a foreign speaker didn't understand them they would instantly repeat, using one of the "ordinary" phrases.

An interesting illustration of U.S. colloquial use occurred at a public restroom on a highway. A woman with two young boys, perhaps ages eight and four, was waiting outside the door of the men's room, and was a little concerned because the four-year-old was still inside. She asked the eight-year-old "he's been a long time, please go find out what he is doing in there." He returned and said "He's going to the bathroom in there."

I agree with Thomas and Su.Ki. that many of these are rare and some quite vulgar (there are a few worse ones I didn't bother with).

My point was to list as many as I could just in case you heard it and were wondering what the heck you are being asked. Some of them are more likely to be heard when the asker is drunk or you are at a particular venue. For example, here in Canada we have outdoor concerts and they usually truck in a bunch of portable toilets. These are known as "Johnny on the spots", "Porta potties", "Portable toilets", etc.

It's also quite common here to go camping and the outdoor facilities are usually called outhouses.

Again, non natives (and polite natives) should stick to the 'normal' list and the other suggestions given by Thomas.