I know the show is set up to never have Tom Welling in the suit, taking the mantle of Superman - but how could he, even if he did? Lex certainly knows who he is, and all the other non-powered characters do as well.
Would the Superman of this universe actually have to wear a mask?
"I'm not smart so much as I am not dumb." - Harlan Ellison
Lets be honest any one who knows Clark would know who Superman is as soon as he appeared. The whole Lex thing would be a problem as he should be able to recognise him as well but hey even in the comics where lex has a 12th level intellect he doesn't know and Lex has crossed paths with Clark a few times. Its one of the many wonders of the mythos, perhaps the costume and gel'd hair is what makes it not so noticeable. A flying man with spandex covering his body and underwear on the outside probably takes the attention away from his face who the fuk knows, I dont.
Lex & the others would certainly notice it's him but let's just hope it gets to that point. Not having him become Superman is a waste of having him go through all these lessons & trials.
__________________ "It wasn't even about the eggs. Quite frankly I like the eggs, I don't have no...problem with...It's just there's always been a lot of tension between me & Lois. It's not so much as I want to kill her...I just want her...to not be...alive anymore. I sometimes wonder if all women are this difficult. Then I think to myself, wouldn't it be MARVELOUS if I turned out to be a homosexual?"