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.
Conventions for 2015 (so far...): Momocon, A-Kon, Otakuthon, Sac Anime
Cosplay line-up: Mayoi Hachikuji (Bakemonogatari), Nona (Death Parade), Nagisa Momoe (Madoka Magica)