Do straight guys notice in gym or locker room gay men are checking them out?

Nah, not really, as long as they’re discreet and subtle about it. I honestly don’t care. The only time it gets uncomfortable is when someone’s being super weird about it—like staring too much or kind of following me around. That’s when it feels creepy. But if it’s just a quick glance or something I don’t even notice, whatever. Also, to be honest, sometimes someone’s looking at you, and they might not even be gay, so it’s not worth overthinking.
 
Yes, I notice. And if it’s a brief look and they’re not acting creepy, I typically don’t care.

What’s creepy? Well, a guy once asked to exchange numbers while I was showering.
Fortunately stuff like that is extremely rare!
 
Assuming the OP is talking about a male locker room. How does one tell who is Gay ?

A curious quick 1 -2 - 3 second glance doth not a gay man make :cool:
Likewise how does the OP knows the orientation of the person he is staring. He could be starting to a gay men who doesn't have any mannerism and missing the opportunity to talk (with clothes on) and realize of his orientation and get it out of your system if it's not viable.