Now I, personally, am not bothered by being addressed as a 'guy', but then I've always felt 'one of the guys'. But then, Ruth doesn't have my gender identity issues, so if she refuses to be a guy, I'll do my best not to address her as one. [Note how I said I'll do my best. I know I'll often slip. Feel free to cough loudly when such is the case.]
Aside: I spent at least 15 minutes trying to figure out how to call the chatgirls then, because "y'all" - I've used it, and it made me slap my head every time I cought myself at it - is just far too American for me. Yes, I'm a language-snob. I'am fully aware of this.
Lastly, Ruth, if you don't want to be seen as a 'girl', I'll do my best not to call you one, but I am a girl, and I'd like to have the right to identify as one, thanks. You made a good point about the 'guys' thing, but I personally don't see the harm in identifying as a girl even though I'm 20. I am not a woman. I'm a girl.