I admit I'm not the Constantine expert and had to look it up but I think the Vertigo version of Constantine's been Bi at least since Brian Azzarello's arc Ashes & Dust. But I've heard it was rarely referenced after that.
But I think the new 52 version (or was it Rebirth) he dated a black guy with 2 daughters. I think new 52 John is more open about it.
I think Constantine's old junkie friend Gaz from the first couple issues of the vertigo series was a gay pedophile. I don't think John partook but I always thought it was skeevy he knew what Gaz was up to in Morocco.
(when did Dawnstar go gay? Did she get bored waiting for Wildfire?)
When I read the original post I didn't get what all those characters were supposed to have in common. I mean I knew many of them were gay but there were so many that weren't, as far as I knew. Madame Xanadu? Maxima? Wonder Woman? Dawnstar? Harley? Ivy? When did all that happen?