I have Feral cats/kittens. I will have to trap them to get them to get spayed/neutered. So I will not be able to have a set time or day. It will depend on when they get trapped. Can I still bring them in to get spayed/neutered? At low cost?

You should call and explain your situation to them. They can make special arrangements for special circumstances.

I had to drop our cats off at 7 or 7:30 in the morning, and pick them up at 5 to 5:30 in the afternoon. However, I imagine if you talk to them, maybe you can come to an arrangement. However, they get busy. They are low cost after all. Good luck!