I call bullshit. If that's true how come they never want to have sex. You can't just walk up to a hot female and say "wanna fuck" but that would be a dream come true if a woman ever did that to a guy.
Women are obliged to maintain the illusion of not being complete sluts, but they are every bit as keen on sex as men and probably more so since their libido doesn't hinge on how full their nuts are. Also, I'd guess 30% of women are down with bi sex if they feel liberated by a scorn-free environment. It sounds like you're dealing with women who are uptight and have their guard up for whatever reason, maybe the environment or maybe your behavior.
Women aren't as coarse as men generally and they are easily put off by stupid male behavior so it's unlikely that the wanna fuck approach will yield results, especially if you approach her without any indication that she's interested. A woman's libido will rise and fall with their cycle, but most of the time the only thing single women are thinking about is who is going to fuck them next and how it's going to happen. Young ones at least. Older ones are a little more complicated.
Of course, the goal shouldn't be to get laid. It should be to find a woman that you enjoy having around even when you're not fucking her.
