I appreciate the feedback, and I don't consider 18F to be "highly PC" (at least to other places I've worked). I guess personally, while "guys" is a common term, it doesn't seem like a truly gender neutral phrase - I wouldn't ever call a woman a "guy," so why would the plural work?
In reading further about this just now, one interesting note is that "guy" is not neutral, and "guys" in the 3rd person is not neutral, but "you guys" (the second person) is used more generally.