Stingrays at CC are in a protected area with nets. Yes, there are a few in the snorkel and family beach areas that got in as youngsters and grew up (same as the barracudas!)
We were told by the animal care people on CC that when they knew the island was going to get hit by a hurricane, they took down the nets knowing that the rays could fend for themselves better in deeper water. Within days or re-establishing things on the island, all but 2 of "their" rays had come "home," and within weeks, all had returned. Seriously, why not? At CC they are fed, have social interaction, etc. In the big blue ocean, they have to fend for themselves.
Yes, the rays at CC are quite used to interaction and handling, as are those at Stingray City. At Stingray City, nothing keeps them there--they are there because they want to be.