I've been into Yuri for ages, and it does seem like a lot of guys like Yuri because "omg hot girls" but there are other female Yuri mashabiki out there, like me! I've always wanted to be a member of a female Yuri shabiki club though, so I don't feel so weird, in a sea of fanboys... Hi from a fellow fem Yuri lover, though!
Probably most of them, but it's like how a lot of girls are Yaoi fans. Anywho, I myself am a girl and like both, though good old hetero romance is always appreciated as well. (Sorry if that seemed an insensitive way to refer to it ;-;) Bullt like already mentioned, there are definitely some female yuri fans.
I'm a male and a yuri fan, and from what I've seen from interacting with other people is that most yuri mashabiki are female (or at least females will let others know zaidi than males will). I haven't really seen males that will openly admit they are yuri mashabiki in person, but it's always reassuring knowing there are other male yuri fans. Either way, I wouldn't say I feel out of place, but I am hesitant to bring it up sometimes, which is sad.