Speaking from experience - Hellocosplay is horrible and you should avoid them at all costs. They steal their pictures, their costume quality is abysmal, and their customer service is just sad.
Don't waste your money.
Conventions for 2015 (so far...): Momocon, A-Kon, Otakuthon, Sac Anime
Cosplay line-up: Mayoi Hachikuji (Bakemonogatari), Nona (Death Parade), Nagisa Momoe (Madoka Magica), Menma (AnoHana), Tsukihi Araragi (Bakemonogatari)