Most Helpful Guy
Well I'm 6'1, so I prefer taller girls. That being said, I wouldn't even consider 5'7 to be "tall"... just average. You don't want to date any guy shorter than 5'7 anyway because chances are that they'll have a wicked case of Napoleon Complex, so stay away... trust me.
Regarding your hair, I also personally prefer brunettes. I couldn't care less if it's straight, curly, etc. If all the girls in your group have straight hair, then it's good to stand out... you'll draw more attention. So overall, I'd say you're good to go... nothing to worry about.
If you were a red-headed ginger with freckles and no soul, then I wouldn't be quite as generous haha... try to put it in perspective.