Assume you won't be recognized...and then go ahead and do it anyway.
I mean, if people catch on that you're from Code Geass, that's a good start, and the KoR costume is pretty distinctive for that.
Katsucon 2015 Costumes
Costumes: Trisha Elric (FMA), C. C. (Code Geass) - cart version, Seras Victoria (Hellsing Ultimate) - pink coat
Costumes In Progress:
C.C. (Code Geass) - artbook empress version
Mjölnir (The Avengers)
Curufin Son of Fëanor (The Silmarillion)
Cons: AnimeUSA '09, AnimeNEXT '08, '09, CostumeCon '09?, Katsucon '08, '10, '14, '15, Otakon '12, DragonCon '15