You are "not supposed" to have real weapons.
While there are some that flaunt the rules, and some that get away with flaunting the rules, there is a no weapons policy. This is true at nearly all cons, though some are more flexible than others about enforcing it.
The San D ComicCon rules state it on their homepages and their booklets they send out or you can pick up in comic shops. Check the costume guidlines.
If you buy a real weapon from a vendor, they are supposed to wrap it up in plastic and tape, or a box, and you are supposed to leave the con and take it to your hotel room or car ASAP.
If security sees you have a real weapon, they can ask you to leave or maybe confiscate it. If you are getting carried away with a fake one, they will do the same thing.
Even with a fake weapon, I would suggest avoiding waving it about. Most true cosplay/costume fans make a fake weapon to avoid any risk of injury when wandering the con floor. Anyone could bump into you by sheer accident, due the crowds, and all the photo-taking that happens. And if you are wearing masks or a bulky costume this just increases the risk. It's not worth someone getting hurt.
I've seen some very nice replicas made of safe materials over my years of going to conventions.
If you enter the costume contest on Saturday night, the Masquerade, you are permitted real weapons if it falls in their guidelines for the time you are on stage.
You may disagree with me about a real weapon needing to be a part of your costume, but as a student of iado I have a distinct view of safety and respect with weapons, and as a part of a possible cosplay group next San D Con myself, I assure you I will be carrying safe fake weapons.
On the other hand, best wishes with your costume work! I enjoy seeing them all so much I am finally going to join my friends in their costume fun.