I have long straight very fine hair that reaches past my tailbone and I keep it in a single braid down my back to ride. When I get to work, I unbraid, brush, fluff and clip it in some kind of bun. There is a shower at work but usually I clean up with baby wipes or at the sink...my hair dries quicky (a hair dryer stashed in a locker would be good though) and in a few minutes you can't tell I rode to work.
Short hair, depending on the style, could be easier to maintain I guess, but my hair doesn't suffer too much from being under a helmet and a little sweaty since its straight and pretty flat anyway-lol! If you had hair that reacted to humidity by getting frizzy you may have more of a problem
I wash my hair in the evening when I get home then and I'm ready to go in the morning.
Good luck!