There is a specific Stingray City site. There is also a nearby site called Sandbar where most of the snorkeling is done.
The dive is all about the interaction with the Stingray's. As long as there's any squid being offered, you'll pretty much get mobbed by them. It sort of feels like being smothered by a muscled mushroom. Our dive was called on time (45min) because everybody still had air.
I don't know if it's true, but I've read somewhere that since the Irwin incident, only the DM's handle the bait now. Which might be better, several years later I've still got traces of a Stingray "kiss" on my wrist.
The dive takes place in a flat sandy area with a few small coral patches nearby. After the squid was gone (the rays immediately move on to the next boat) we found the resident Moray, by moving slowly I was able to get within 2' of him w/o upsetting him. I think he was hoping I had something left for him.
We were on a diveboat but all the kids in one divers family snorkeled with us. At 15' they could stay down long enough to have a good experience.