Is Val bisexual?

I have to admit that some of his mannerisms and dialogue did give me cause to think the same as you. I think it's more a case of he's adopted some similar communication patterns to Armand and Albert from being raised by them.

I think that Val said "It's a girl," because maybe he knows that Armand and Albert maybe had hopes that he was gay or like you said bisexual.
I liken it to Diane Keaton's character in "The Family Stone" when she said that she wanted all of her sons to be gay that way they'd never leave her. *shrugs*

"Do you even remember what you came here to find?"

That whole scene was to throw the audience off and make it seem as this was some secret meeting between lovers. The line "it's a girl" was said to throw the audience off even more. The older male becomes upset and you get the impression he feels betrayed but then later the hoax is revealed the he is called Pop. I thought it was very clever!

I don't know if he was bi-sexual, but he was a rude, obnoxious brat.

I think that was put in for an audience that may assume that because Val was raised by a gay couple he must be gay too.

I think it was supposed to be like if a his parents were both hardcore Christians and he said "She is Jewish". This was just with the gay aspect.

Come visit my

No. Gay marriage was in the news around the time the movie was being made, so they wanted to acknowledge that same-sex marriage existed. But, it was also a very controversial issue, so the gay couple in the don't intend to have such a wedding for themselves.

I am more curious how Val has job offers prior to get his University degree, or how he managed to start dating a girl not yet 18.

Remember right up to that point, the scene was being played as if Val was Armand's lover, given all the clues they were throwing out. I think the "It's a girl" was supposed to add to that shock because it wasn't revealed that Val was his son until immediately after he says that.

(For what it's worth, I'd much rather think he's bisexual. :-) )