Or kilometre?
Would Joe Taxidriver say “fifteen kilometers” or something abbreviative, like “fifteen clicks?”
(For a book I’m trying to write. Probably gonna end up cheating and using miles…)
Clicks or “kay’s” (phonetically speaking).
Or, “Hey mate, how far until the nearest bottlo?”
“Fifteen kays buddy”, or “Fifteen clicks”.
Kay/s is probably more common though (speaking as a southerner, it might be different in diff parts of Aus).
Edit: would not be WRITTEN as kays though, would appear in the written word as k’s.
I’ve only ever heard kays in NSW.
“Kays” in W.A. too.
Ks, though either will work
In Strine, when in doubt chose the abbreviation of the abbreviation.
Or abbreviate and then add “ie” or “o”, e.g. “chucking a sickie” (taking a leave of absence from work and attributing it to sickness); "I’m going to the pub this arvo (attending a public house this afternoon).
We love to abbreviate but can’t leave well alone, hence the extra ie or o.
“15 minutes, but if ya chuck a u-ey and take the left at the milkbar, you’ll be there in ten”.
I’m rural. We give distances as a unit of time 
I do agree with the consensus that it would be k’s.
Yep, k’s. Or it might be singular, as in a couple of k. Unless it’s a 100Km in which case it’s a hundy.
Queensland would definitely be k’s as well. As kambuckta has said, clicks would be equally normal.
With the cheat of using ‘miles’, that wouldn’t necessarily be wrong, but the speaker would either most likely be older (say >50 years old), or providing a non-specific response as in ‘That’s miles away’
Never heard clicks used by anyone in NSW.
Really a cabbie, if asked how far to somewhere 15Ks from here, would say, “About 40 bucks mate.” And after a long slow look up and down would add, “You got that much onya?”
Interesting. Here in Canada, we tend to use “kay,” in the singular always.
“How far is it to Sault Ste. Marie?”
“About 765 kay.”
“I’m out of White River, eastbound, about a hundred kay.”
“I drove 130 kay on the 401, and didn’t get caught.”
“I get 500 kay to the tank.”
But never “kays,” or “klicks,”
Others may differ but I’d say that in Oz that “kay” is predominantly used for monetary values
“How much did you pay for that house in Sault Ste. Marie?”
“About 765k.”
“I paid 500k for that tank.”
Always singular.
In South Africa, it varies by speaker - but if forced to guess I’d say “kays” is more common for English first language speakers (it’s also what I use) and “kay” is more common for Afrikaans speakers (My mom uses it - I was raised bilingual, but never use Afrikaans settings as a default), It may be because the Afrikaans plural for kilometer is … kilometer.
Oh, and never “clicks”, that would sound like an Americanism to me - or more specifically, something from the US military.
I’m a Canadian who says clicks. I did live in Australia for a year in grade 7 and am not sure if I picked it up there or in western Canada or by virtue of being an Air Force brat. If I did pick it up in Oz then it would be one of the only fair dinkum Aussie-isms that ended up sticking.
You coming the raw prawn?
I hear clicks very rarely, it’s normally kays.
Edit: Miles still turn up in idioms, such as “we can’t walk there mate, it’s miles away!”
¿ɹǝpun uʍop ɯɹoɟ ɹǝdop ɐ ƃuıssǝɹppɐ uǝɥʍ uʍop ǝpısdn ʇsod oʇ ǝsoddns ǝɹǝʍ noʎ ʇɥƃnoɥʇ ı
“That’s not a kilometer. This is a kilometer.”
Don’t get aggro this avro! I’m just being a bit of a bastard. 
Keen! Fun answers! We “do a u-ey” in California, but I’m gonna adopt “chuck a u-ey” 'cause it’s so much fun to say. (Also, thank you for all the eucalyptus trees. I love 'em.)
My style in writing this character is mostly to downplay the dialect, and keep it mostly to “standard English.” But a few touches of dialect, without overdoing it, should help (?) to establish character.
No “Ridgy didge” but maybe “no hoping” once or twice.
Cheers!