I would actually venture to say that female are more likely to ride coasters than males, especially in the jr high/ high school range. If a young lady was scared of a ride, she could get on, scream her head off and no one would think much of it. But if a dude did the same thing, he would be open to all types of belittlement. Therefore a lot of dudes play it "cool" and spend more of the time playing the games (basketball mostly) and skirt-chasin'.
At least that has been my observation. I think the websites and "organizations" are male dominated simply because more men take coasting "seriously". Ask around in your local circles. I'd bet that there are more brave women than you might think.
lata,
jeremy
--who thinks the answer to the orignal question is obvious ;)