So, when I see short hair on a Mexican woman, it means a lot more to me than on an American or Canadian woman. Young women with short hair often don't feel the necessity to conform.
What does that mean for your characters? Assume that readers judge our characters by their outward appearances just like they do in real life. As soon as the reader reads "short hair" or "long hair" they immediately form an impression.
Now, we can go two ways with that:
1) our characters can appear exactly how we want them to be
2) or our characters can appear one way and defy the norms.
That's up to us. But, until we understand what impression we give by our hairstyles, we can't begin to know how to portray our characters. Also, we wouldn't want our readers to judge our characters by their covers so make sure you remember to show them in action rather than solely rely on description for reference.
Have any character's with wild and wacky hair stood out to you? How? Has the first impressions turned out to be incorrect?