Hm, since cosplay just stands for costume play, shouldn't we refer to the act of dressing up as our characters as cosplaying, but then talk about the outfits themselves as costumes, instead of cosplays? Like, "I am going to cosplay a character from dbz this year. Do you have any dragonball z costumes?" instead of, "Do you have any dragonball z cosplays?"
Obviously it doesn't really matter, since everyone at the con will know what you're talking about if you say either one, but when talkin' to muggles, the distinction would probably help.
Personally I don't really get sqeamy about telling people about my costumes. I'm one of those "thinks he's better looking than he actually is" and "has people skills" people, so I say I'm a total geek with a sense of pride!
Word.