You could consider a taxi tour. We've not rented in Mexico, but I know their liability laws are different than the US. If you rent a car be sure to get insurance. If you are in an accident you have to pay for damage first and then they worry about fault later.
A Bad Day At Sea [with power] Always Beats A Good Day At Work
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014