I have an answer for you MrsSpamtastic, I usually have to suit up at the event and I bring helpers. Even though the Cybermen are foam they still require at least one person to help dress you as well as watch over you as you wander. Professionally we call these people handlers or wranglers, my wife is mine and I am hers when she wanders the floor as the giant adipose, the limited visibility is a major issue and having a partner or friend to watch your back is an absolute must. I will usually carry the costume in bags or boxes, then I will find a somewhat secluded area to get dressed. If you can put on an under suit that covers your body head to toe and helps cover your nakedness when dressing outdoors. I have friends that have dress up tents they bring along to events. Hope this helps.
