I have a shower at work, luckily.

I have had both super short (right now it's less than an inch long) and super long (braid down my back) hair while biking. Personally, I look better with long hair. A helmet does NOTHING to my hair when its long since my hair is both curly and thick. In fact, nothing does much to my hair when it's long, even me! It's got a mind of it's own and I'm just along for the ride. The problem for me was that it was HOT and that my helmet always felt too tight.

Now that my hair is super short, it looks ridiculous when I take off my helmet, but one or two handfuls of water through it and it's passable. It's way cooler feeling though, and I'll take that over how I look any day.