If anyone has cruised on the Carnival, RC, or NCl cruise lines I'd appreciate your input. Specificially the Western Caribbean cruise.
What is the dress code for dining like?
What are Sea excursions? Any suggestions for what not to miss doing?
Can you wear new jeans in the dining rooms on any of these cruise
Do any of these have golf or rock climbing walls?
Thanks in advance.

I traveled this itinerary about 7 years ago and will be going again in July. I traveled on Carnival's Imagination and LOVED IT! To answer your questions, the dress code was mostly relaxed with the exception of the formal dining room. Being my first cruise, I didn't want to get myself in trouble by wearing the wrong clothes. There were two nights where nice evening clothes were a must. I dressed in a nice dress and the men wore suits with ties. The other less formal nights, we toned down with slacks and a nice blouse, men were wearing dress pants with blazers and slacks or just nice shirts with ties. There was one night where you could wear casual clothes to the formal dining. Check the Carnival Caper newspaper you get each day and it will tell you what night that is. I never saw them turn anyone away due to the way they were dressed. The formal nights they paid attention to what people were wearing, but other nights you might be able to get away with nice jeans. Ask your travel agent or call Carnival's number and talk to an agent. They will answer any questions you may have.
If that is too formal for you, there are other alternatives to evening dining than the formal dining room (i.e. bar and grill on Lido deck, some ships have alternative dining rooms, pizzeria, room service - you did pay for it). .
The shore excursions were excellent. In Cozumel I went on a Sail, Snorkel, Beach party excursion. If Cozumel is on your itinerary, I suggest snorkeling. There are lots of coral reefs to explore that are beautiful. It was my first time snorkeling and I swallowed my fair share of salt water, but we were able to go at our own pace and enjoy ourselves. In Grand Caymans, we swam with the stingrays at Stingray City. I have been stung by them before and was nervous about being in the near vincinity of them, but they are very tame and absolutely beautiful. A once in a lifetime experience, so go for it! In Jamaica, if you can climb I would suggest Dunn's River Falls. Again, absolutely beautiful! You go with a guide and hold hands with others, which at first I was unsure of, but it made it much easier to climb and you got to know a new friend. Beware of the Jamaicans because they will try to peddle their goods to you alot. If they are bothersome, ignore them and don't look at them. They will go away. Just say, "No thanks Mon!"
The ship was great! Very clean and neat and the staff were wonderful. There was no rock climbing walls (there may be one on Royal Carribean's ships) but there was miniature golf courses to play. I was never bored on board!
I hope I was able to answer your questions and wish you a great time on your cruise. Bon Voyage!