After visiting Cancun a number of times, and looking at other blogs too there are a number of tips for fellow travellers to Cancun, Mexico.

-(thanks to Dave’s blog) Book to be picked up at the airport.  The airport is such a racket, and you will pay a lot of money if you do not a reservation.  It is set up so that the locals reduce your load of dollars.  Avoid that, and either have a cab waiting for you, hotel transportation waiting for you, or you have a rent-a-car to go to.

-plan to spend an hour with a cheap rent a car place.  And expect to get shoddy cars. Message: spend some money on a decent car.

-Wear a T shirt if in the sun, or at least some sunscreen.  It is a must.

-Cruises:  There are some great deals if you look for them. Check out the tour guides outside the hotels as they can sometimes provide great bargains.

-Take your lonely planet (or whatever else) guide with you.  Information is sparse once you are there, as far as adventure locations are concerned.  Do make a friend with your waiter and cleaning lady, the investment will pay off!

Here are some great resources:

http://www.sirpi.org/2007/12/25/how-to-find-a-great-all-inclusive-mexico-vacation/
Great post on how to find a all-inclusion mexico vacation.

http://www.summercampscorecard.com/vacation-tour/mexican-cruises-on-the-riviera-to-cabo-san-lucas-cancun-and-acapulco.html
Read about a cruise vacation stopping in Cancun.  Great post.