We are leaving in just 3 days for the Mexican Riveria on The Spirit - One Suggesion: We found a shore excursion company that actually works with Carnival and does some of their tours. However, if you book through the company directly you save a ton.
They are very conscientous and work with the ship itineraries to make sure your tour does not conflict with departures, etc. We had to change all of our tours due to the Splendor problem and they were awesome. We even changed one tour to something cheaper and it resulted in a refund to us. We got the refund quickly and they were just awesome.
Hope this helps. Have a great cruise!