muntdefems: As the OP has been answered, I'll just go and ask it since I'm genuinely curious: once, a (masculine) guy from Texas told me that 'guys' is a gender-neutral vocative, or at least it's now used as such. As in, I could say "hey, guys" to a group of only females and they would see it as OK. Isn't that so?
EDIT: I see toxicTom agrees with that acquaintance of mine. :P
Unless you want to go with the (very Southern/country-sounding)
you all/y'all (or regionally variants like
youse, most of which are also widely thought of as "uneducated"), there really is no existing substitute for gender-nonspecific
guys that isn't needlessly wordy or stilted-sounding. (Personally, I often address mixed groups as
folks, but that would probably be considered too rural or...well, folksy for most people.)
When addressing a group consisting solely of females,
gals,
ladies and
girls are all options, though each has its own issues.
Ladies is probably the least objectionable of these, though some will still take manage to take offense. (At the museum at which I work, I once overheard a member of a party of women that I had addressed as "ladies" remark to one of her companions, "At least he didn't call us 'guys'." I would've loved to ask what term she would have preferred over either of those, but I figured it would be more prudent to glide past that topic.)
On a tangentially related note: In conversation, I once had a female co-worker exclaim at me, "Suck my dick!" (said in the same mock-offended tone that one would tell an acquaintance, "Screw you!"). That gave me pause. :D
Not sure what it says about me that at first, my brain parsed the name of the first respondent to the pictured post as a misspelling of "analrimmer" =|