I pretty much agree with Cav, though I do think it's just bad manners to do so when we're together. We all stare (not just a man thing at all) but I don't stare when I'm with my hubby, I stare (and comment) when I'm with female friends.
And I know it's not just me. But we both feel like it's impolite to do so when we're together, especially a "turn his head staring" kind of thing.
Now, we comment, to each other, all the time. (We're actually really bad that way.) I mean, there are people who are hard to ignore. If a gal in 4-inch heels, a skirt cut up to there and a shirt cut down to here sashays by, everyone's gonna notice and it's artificial to just gaze into the middle distance and say "What? Who?" We just snicker or make mean comments in sign.
Same if a guy saunters by with slicked-back hair, skin tight leather pants, and a mesh shirt. (We used to live in L.A., we saw plenty of both types, believe me.)
The point is that we are both inveterate people-watchers, but we tend to share the people-watching.
We have a friend who is TERRIBLE about this, and I've gotten mad at him on his wife's behalf (she's gotten mad at him plenty, too.) He's the kind of person where, when talking to him, I have to do a little curstyish dip so that he is again looking at my eyes rather than my chest.
He's a sweetheart, he doesn't really realize what he's doing, but he does it ALL THE TIME. I do think there is a point at which it becomes unacceptable, especially in the company of the spouse.
Good luck!