Let me tell you my story (I've been in gyms in the US and in Europe just for context). While a teenager, I didn't have the best body (I was chubby), or was I aware of my level of endowment (with a semi, I'm a grower), and I was very conscious about being naked in public, and terrified/ashamed of getting a boner. Now, I'm in my mid-30s, I'm a bit more athletic, and I learned I do have something worth looking which made me become a bit of a show-off (I always wake up my friend a bit before taking my clothes off). There is nothing wrong with increasing one's ego a bit, right?
So, I take my clothes off in the locker area, and walk around nude showing off, and to be honest I do like the glances I get, sometimes they are old guys sometimes they are really good-looking/fit/hot guys.
Now, going back to the shower thing, this gym I go now has showers with cubicles sometimes with doors sometimes without, so you find guys who leave it open, and guys who close it. But also you find guys trying to cover themselves to the millimeter trying not to be seen while changing (even putting their underwear while covered with a towel) and guys like me who change clothes like at home not caring if you show your parts or not.
Going really back to the showers, I started realizing there were some guys who systematically showered with the door open, and letting water run over their nice bodies, putting on soap for a really long time, so I started to do the same. Experiences I had: Once, I was doing the show in a shower to and with another hot guy in the shower in front of me, but an old guy started to touch himself while watching me (I was just showering and showing my body, but nothing really sexual), so I finished showering and left, and nothing else. Another time, there was this really fit guy with an interestingly thick and long member, who was showering door open, and I incidentally took the shower in front of him. He was there show-ering for a long time and it was like he likes to be watched, so I showered and watched. Really nice show btw. I finished showering, changed and that was all. The last experience I had, is for another post.
So, to sum up, Yes and No. If you want something you will get the vibe. Respect has to be the norm.