I'm a bisexual tomboyish female. (And to clarify, I don't consider tomboy to be its own gender, so I guess that means I'm not-trans/cis/whatever.)
And from a quickly looking through the various sexual orientation groups on FA, it'd appear that there's indeed more gay people than straight in the fandom (~5642 straight and ~9681 gay).
There's also ~2277 furs identifying as some form of trans, ~298 genderless, and ~2472 identifying as genderfluid. Don't think there's any group for cis-people, so can't really give a number on that, but seeing as there's supposedly close to two million accounts on FA, I'd imagine cis-identifying people to vastly outnumber the amount of transgendered ones.
So, at least for FA, there'd appear to be more gay than straight people around, at least ones that are actively watching the groups and stuff. (But then again this isn't really the best thing to go by considering how few registered members there are actually watching the groups)
But interestingly enough, a dating group (also on FA, and open to all sexualities) has 87 ads posted in the straight-section and only 2 in the gay one.
Even with all the various LGBT-sexualities lumped together, the straights are in the majority there, surprisingly enough.
As for this site, there's been a few polls throughout the years, and the results might also come as a bit surprising:
https://www.thefurryforum.com/forums/index.php?topic=15426.0;viewresultshttps://www.thefurryforum.com/forums/index.php?topic=24597.msg1128194#msg1128194https://www.thefurryforum.com/forums/index.php?topic=29745.msg1533558#msg1533558With the exception of 2014, straight "on it's own" was in the majority, but lumping all of the LGBT together, they outnumber the straights.
(There's also been at least one gender identity poll as far as I can remember, but I can't seem to find it anymore.)
Then, this would also suggest that there are more straight than gay furries around, but that there is a much larger concentration of gay people in the fandom than out in general society. (Tho again, lumping all the LGBT together they still tend to outnumber straight people. And in many cases, most seem to identify as bi)
http://en.wikifur.com/wiki/Sexual_orientationIn short, there seem to be more straight people around than people tend to think, but as the concentration of various other sexualities is higher than in general, it seems like there's hardly any straight people around.
Not really proper evidence of anything, but it's got numbers and stuff I suppose.