Personally, seeing other people express their affection doesn't normally bother me. If things start to get slightly weird I can always just turn away and ignore it.
Myself, I can admit to being a little clingy... But honestly, if I find someone I truly care about, I don't care how ridiculous I look in public as long as I'm with that special someone.
Unfortunately I'm no longer with that special someone... And ironically, it may have had something to do with my clingy-ness >_>. *sigh*
Well, I can keep dreaming.
Short version: Public affection is A-OK with me (as long as things don't get too weird if you know what I mean)
Oh, and for reference, I'm Male, age 19.