I'm going to have to maintain my opinion that being in a populated area where most people are decent human beings is better than going down a dark alley in someplace like downtown New York.
Yes, there are assholes and creeps at conventions, but there are more non-assholes plus security every corner, at least at the conventions I attend. At the cons I go to, security is very good at their job, and I've only ever run into one creep out of the thousands of people I've seen there.
Even so, like I said, I know how to handle myself. I make sure to be with a trusted friend at all times. If someone makes me uncomfortable, I tell them to back off. If they don't or they try anything, I scream, kick, punch, run, find security, call 911, etc.. I keep a charged phone on me at all times. Yada yada.
Fandom Fest 2014 cosplay: Kiki (Kiki's Delivery Service), Sayaka Miki [mermaid] (Madoka Magica)
MCM London Comic Expo cosplay: Kiki (Kiki's Delivery Service), Nagisa Momoe (Madoka Magica)
ALA cosplay: Kiki (Kiki's Delivery Service), Snow White (Zombie Panic in Wonderland)
2015 conventions: Anime Los Angeles, Anime Central, Japan Expo