I did a dive at Cobalt Coast a couple years ago and the diving there is not that great. They have no beach so its a rocky entrance or a ladder. They have a dock too so getting in/out is not too bad. But the reef there is not really very exciting. There is some coral and a few fish but nothnig spectacular. It's a long way to the wall, 100yards or more and even that is not a very good wall dive. No swim throughs or any big sponges or anything. I think that part of the island got hit really hard wth the hurricane several years ago and has not receovered yet. They are kind of in a rat maze of twisted windy roads part of the island and very difficult to find. The food there is okay but I sure would not want to eat it for days in a row. I didn't see the rooms but I have a friend that that lived in Grand Cayman and said the rooms there are really small, not very clean, moldy...
They have a boat dive there, Divetech but I have been diving with them and after being taken to shallow sites and not going to the north wall (even when other boats were going there) because they LIED and said the weather was too bad, my husband and I ended up canceling the next few days and going with someone else.
You would be thousands of times better off going to Little Cayman. The diving is not even close by a mile! Stay at Pirates Point or Southern Cross and it would not even really cost much more. Or if you really want to stay on Grand Cayman, there are affordable hotels and condos and you could dive with a great company like Neptunes, Off the Wall, Wall to Wall... there's lots of them. And you could shore dive some of the east end places like Babylon and Anchors Point. That way you get to see all the best sites, try some of the great restaurants and not be stuck at one place the whole time.