It's been a long time since I did a workout at the Y, but....l used to do it while I traveled, since Y's are cheap day use gyms.
The Y's I have used always had a separate free weight room that was virtually EMPTY. Almost everyone at the Y was in the cardio room, with a couple in the room with the machines, and a host of old folks in the pool.
I could have grunted, sworn, or crumbled under a bar without anyone noticing.
No one there would have noticed if I was doing any O-lifting.
Now...your standard 24 hour fitness might be a different story.
Mostly, I'd say that if a gym is opposed to Powerlifting or O lifting, you'll notice it by the signs all over the place that say things like "No Chalk" "No Grunting" (seriously) and "Do Not Drop Plates"
I've also been places where you'd expect them to be against it and they aren't. Like..the Las Vegas Golds. The place is packed with cardio gear, and filled with slim, beautiful people..dancers, show people... But in the back corner there's a Power Room that has boxes with chains, 2 power racks, boards for board presses and other PL accessories.
Really, the best thing to do is to check out the gym you are thinking of joining and ask plenty of questions.
But if it's a question of using an occasional gym while traveling, I think the Y is a good bet.
dian in spokane