We (5 of us) did the day to Blue Lagoon including the Stingray City trip. We thoroughly enjoyed it. That said, we are not avid or experienced snorkelers and for us it was our first time. The water was a bit choppy the day we were there but the employees are in the water and get the stingrays up where you can touch them. There are also a pile of other tropical fish around. Someone asked while we were there how much the visit to Stingray City was if you walked up and were told $15.00 per person. I can't remember how much the day shore excursion alone at Blue Lagoon alone was/is but you could do just the Blue Lagoon trip and some of your group do the Stingray City while others pass. Until you go you don't really understand the logistics of where this is and what is involved.
It is about a 40 - 45 minute trip with a quick stop at the dock on Paradise Island enroute (not tooooooo far from the Atlantis Hotel) and then once on the the Blue Lagoon you are led to the Stingray City which is at the far end of the island. Its a fair hike and IF there is a large group I'd personally suggest waiting 30 minutes until everyone else is done. Much quieter (as long as no other groups are in there) and there are lots of things to look at enroute.
I've heard complaints about the food included but I have to say I personally found the food good, plentiful and a decent choice. You get "drink coupons" but be warned it is NOT for the cans of juice or pop directly beside where you get your lunch. It is for cups of fruit punch (No alcohol and someone asked for a rum punch and they do not sell it). The punch was very good and you get two coupons each but don't automatically grab the cans of soda pop or juice figuring its included. We had a great day at Blue Lagoon and for novice snorkelers like us it was great. I think for people that have done a fair bit of snorkeling it may be a bit dull. However Blue Lagoon was beautiful. The hammocks, water and location was great.
Cheers,
Grumbo