"I'd like to hear any suggestions on this. We would love to snorkel in Cozumel because it is the number one dive spot and would really prefer to dive but the excursions look to be SO expensive. We'd like to experience the stingray city "thing" too if possible. "
You should definitely go to sting ray city. I didn't think there was that much of a difference in price but I've seen some reviews of 3rd party vendors in the chat room.
"I have a question about attire. I realize that there are 2 formal nights and we'll need to dress appropriately on those two nights. Asside from those 2 nights what is the normal dress code (my question is basically for Steve)? Can he wear nice microfiber pants and shirt? Does he have to wear a tie? Can he wear Dockers and a nice shirt?"
Dockers and a nice shirt are fine for all the other nights. A tie is not neccesary.
"As for alcohol, can you purachase a drink card for alcohol or is that for soft drinks only?"
Drink card is no longer offered for alcaholic drinks. You can sneak a bottle in your luggage if you want to risk it or you can pay a "corkage" fee (I think it is $9 a bottle). Drink prices are not too bad.