There are really no "gay people" in Inherent Vice. What the book actually shows is a time and place when people didn't feel a need to declare their sexuality one way or the other (or another), when people felt free to experiment and do whatever they felt like at any given moment.
There's Jade/Ashley and Bambi, who met and became lovers in prison, who live together (with a cat named "Anaïs," which is a nice touch), but who also go on double dates with rock musicians, plus Jade/Ashley apparently has some sort of thing going with Denis.
There's Puck and Einar, who live together (also after meeting and becoming lovers in prison), but Puck also has an ongoing relationship with Trillium and Einar considerately steps out when she comes over.
Puck and Trillium get married, with "Einar acting as best man and deciding himself to elope with another groom-to-be who'd been waiting for a bride with what turned out to be cold feet, as, in fact, he discovered with signs of relief, were his own."
(Things end badly for Puck and Trillium, of course, but I think the lesson there is more, "Don't marry guys with swastikas tattooed on their heads.")
And there's also Sloane and Luz, who become lovers when Mickey goes missing, staking out the Wolfmann marital bed as their own territory. Until, of course, Mickey returns and reclaims his position and rights as patriarch of the household. But when Sloane and Luz are together it doesn't interfere with Luz having a fling with Doc (and there's also Luz's possible boyfriend, but that's only Doc's deduction–it's not proved one way or the other). And of course there's also some joking that Doc is titillated by the thought of Sloane and Luz together, though that seems to pale beside his fetish for "Manson chicks."
Nobody declares that they're "gay" or "straight" or "bisexual," or feels any apparent pressure to make any sort of declarations. The only explicit statement at all is Puck's mention of Detective Indelicato's "hatred of homos." Clearly, the open spirit of experimentation doesn't extend to the LAPD.
And this is a specific instance of what Pynchon refers to in broader terms at the end, where Doc is driving through a thick fog and thinks that it might spread and settle in regionwide. "Maybe then it would stay this way for days, maybe he'd have to just keep driving, down past Long Beach, down through Orange County, and San Diego, and across a border where nobody could tell anymore in the fog who was Mexican, who was Anglo, who was anybody."
He wants the fog to roll away and reveal another world, where people are not divided into all sorts of categories but instead can just be people.
This is related to what I've done in my writing. Vicki is gay, but she doesn't make any proclamations about it, and in fact we get through a whole novel with her before we even learn what her preference is. The only time she refers to her sexuality at all (except in private conversation with Jan or Marshall) is in the chapter "A Different Choice", where she calls herself a dyke, but that's to make a point to her mother. Which is "I yam what I yam and that's all what I yam," more or less.
And I guess the flip side is SarahBeth, who does declare that she's gay (whether or not anybody asks), but doesn't see why that should mean she can't have a boyfriend if she wants to.