My 14yr old daughter and I have straight hair (thanks to my Native American heritage). Although....her dad is full Italian and she gets some curl when she hates it.
She has a Chi (pricey but worth it) and the Chi protective products you use with it to make sure her hair is straight daily.
For the most part, we both have very straight hair, however, the humidity does wonders for us and we will take to the hair with a Chi when needed. She uses it daily, I do not need to use it...mine is too straight already.
We both use the Chi silk therapy stuff for afterwards that is nice.
Good luck... We've bought our items at Ulta. Sometimes you get a special coupon in the mail or Sunday paper. The Chi iron my daughter has is about $125.
NOTE: It is the 3rd iron she has had however, it is the one that has lasted the longest. Therefore...she got her $'s worth with Chi vs buying 2-3 irons (@ $40+) to get the right one.
TIME = $$$$