Actually I am of the opinion they would. Okay maybe they'd not say it's lame but they would want to know why the Stormtroopers are unarmed, and why Rex or Jango for example has empty holsters. When people expect to see it on a character they notice when parts of it are not there - even if they are not 100% familiar with everything to do with said character.
I trooped the Download Rock Festival last year without my jet pack after one of the straps of the harness broke whilst I was putting it on. Loads of people notcied I did not have it and commented - usually along ther lines of "Hey Boba! Where's your rocket pack?" They noticed that (but not that my armour is not boba's!
) So they'd notice a lack of weapons.
Personally I couldn't care less about Anime characters not having their huge swords (but then I have no interest in anime) - besides, I couldn't tell one anime character from the next and niether could most of the public. But stick Vader and some Stormtroopers or Clones out there and practically everyone on the planet knows who you are! - minor exageration. And in my experiance practically everyone that comes over wants to be shot, arrested or sabered for a photo - not exactly easy to do if some Jobs-Worth has said "No blasters! No blasters!"
Get your group to get an exemption to the rule or don't attend.
I've walked into jewellers stores in full armour and carrying more (prop) weapons then a New York street gang. If any place has a worry about possible real guns its them, yet all they wanted to do was pose for photos with us!
Okay, America has far more guns then almost anywhere else, and yes someone could decide that their Stargate uniform for example, would look so much better if they took the real gun they happen to have or maybe even just the realistic bb gun. But a little common sense says that the first is unlikely and that a simple check by a member of convention security with firearms experiance would identify any actual weapons easily.
What's next "Errr.. Sorry Darth but you can't bring that in here unless it's made of neon pink foam and squeeks when you wave it about"?