Forgive the foray into spoken English, but I must address yet another example (scroll to the end) of someone going out of her way to be offended by the use of "you guys" to refer to mixed company. This is a staple of amateur restaurant criticism.
Point No. 1: There's plenty of better stuff to complain about when it comes to restaurant service.
Point No. 2: I've said it before, and I'll say it again -- "you guys" is to the more vanilla regions of these United States what "y'all" and "you all" are to the South, what "youze" is to New York and New Jersey, what "yuz" is to Appalachia. English uses the same word for second person plural and second person singular, and sometimes it just doesn't satisfy.
(And, yes, that was me. For the record, I've never met Mr. Sietsema.)