I've had 3 cruise ship stops in Cozumel; tried to dive on all 3, only got to on one (wife likes to cruise in Winter; dove one January, got blown out the 2 Feb. stops). Palancar Garden was okay, but Santa Rosa Wall rocked! Dove with Living Underwater and it was a good experience.
A major issue considering a Cozumel trip is a combo. of the tyranny of choice (so many choices in places to stay, eat, who to dive with) and analysis paralysis (I like to research destinations & understand what I'm doing when I plan a trip; I turn my thoughts to Cozumel and get brain melt-down), cross-referenced with being budget-minded if I bring family (wife, daughter, little girl) - their needs matter and so does the bank account (which makes the 'easy solution' of a nice southern A.I. less workable, seeing as how they want money for all that nice stuff).
Some trips I go solo; some with family. Because Cozumel can be a budget destination and has topside offerings, it's harder for me to justify a solo trip. If I went solo, based on what I've read, I'd probably consider a stay at Casa Mexicana (? IIRC; the one with the very popular breakfast buffet) and see if Aldora or Living Underwater would pick me up nearby. Or I might be swayed by the simplicity plus shore diving option of Blue Angel Resort. Or, or, or...TILT! TILT! TILT!
Richard.