We don’t use “gals” here so “guys” for a group of both male and female or either is common.
I have more problems reconciling with being called “cobber” than I do being “one of the guys”.
I worked with a lot of women in college and they would bristle if I used the word “guys” to address an exclusively female group. Really couldn’t blame them–I’d hardly go to an association of female firefighters convention and address them all as firemen.
Now, all my colleagues in my building/work area are women, so I say “Y’all”, though I do it without any southern affectation or faux accent. It comes off seamlessly without bringing up the gender issue as it would if I used the term “ladies” or “gals”. I also use “everyone” if it doesn’t sound too weird or awkward.
I sometimes even call women ‘dude’.
Yes, that’s the way it works. Sometimes I wish that English had more gender.
Some women are offended by the word “chick.” But it’s probably derived from the Spanish chica. So, there’s also chico for “male chicks.” (Or a group of chicas y chicos.) Equal opportunity!
I’ve encountered the term “Chicano/a Studies”–which is appalling. Bad English, Bad Spanish & not very good Spanglish.
I make it a point to address any (familiar) group of men as “ladies”. 
Ok…so I can use ‘guys’ as a plural?
Or I can’t?
Ok…lets make this easy: How many women here will I piss off if I call the group of people that they are a part of at the time ‘guys’ in a non-condescending, honestly-trying-to-be-inclusive way?
Show of hands, please?
not me.
man/woman
boy/girl
guy/girl
I think the problem’s there. Girl seems to be pulling double duty opposite “boy” and “guy” but brings with it the same implied condescension of “boy.” Let’s check out our options for addressing a group:
“Hey ladies…” -> sleazy guy at the bar
“Hey gals…” -> better make sure you’re not a) wearing cowboy boots or b) a character from a Trixie Beldon novel
“Hey girls…” -> condescending
“Hey women…” -> ahahahaha!
“Hey guys…” -> unless you like one of the above better…
Not me either. I think if a woman gets mad at you for “you guys” then you did something else to piss her off.
“You girls” could be a little annoying, though.
Not me, either.
Heck, I’ve heard many a sergeant address a bunch of us (mostly if not uniformly -heh- male) with “Okay, ladies, here’s the plan…” or words to that effect.
Having endured numerous heated discussions between women over the years arising from nothing but widely varying individual preferences over this very issue, I have taken to crippling my use of the language by avoiding constructions that would require it.
I worked with one especially delightful lesbian cowgirl who called women “gals” with such affection and charm that it changed many hearts. But usually there is just rancor and sour displeasure over the various options. Meh.
Now look here chaps.
I realise that Callie (from CSI Miami) has a lovely drawl when she says “ya’ll”, but let’s stick with the original. If it was good enough for PG Wodehouse…
Dude! So do I. 
If I’m addressing a group of women, I’ll usually say “ladies.” But I’m a woman myself, and it would strike me as odd if a man were to do the same thing. This is why I love “y’all.”
“Folks” or “Ladies”. Folks is nice because it sounds well, folksy if a little old-fashioned. It doesn’t have any baggage associated with it and it works well with a mixed group.
I get frustrated at our language’s lack of genderless pronouns. I wish we had a word that could be used in place of he/she that wouldn’t reveal gender, because it would save us a lot of embarassment and time spent on gender-correction. This is why I like “you all,” or “y’all,” it offends no one.
If someone on a messageboard mistakenly refers to me as “she,” I often wonder what triggered them to arrive at such a conclusion. Usually, I take it as a compliment because I pride myself in being an exception to oafish male stereotypes. Kind of like the warm fuzzies I get when someone mistakenly thinks I’m gay.
“Gals” sounds kinda cheap, like “toots.” I think guys has become largely androgynous, and will grow more so as time marches on.
You can call me guy - even if you are addressing my girlfriends and myself without a male in sight. In Minnesota guys is a gender neutral term and has been for as long as I’ve been aware of it. (I grew up in Kentucky where the plural is ya’all - which I don’t find to be a bad plural form at all - you sound a little like a hick, but that would pass if it were generally accepted, when I got to Minnesota I discovered the plural you is “you guys.”)
Call me “gal” or me and my girlfriends “gals” and you’ll be lucky if all we do is kill you with the nasty look.
I like guys. It sounds friendly, easy, companionable. I have found only a few guys who say “girls” without coming off as superior! And in the Northeast, we are pretty accustomed to guys.