The city as a hop on and off trolly. That will get you to most places. Search for it in google.
The Zoo is a hot spot.
Several ships to see at the cruise terminal.
The airport, downtown and cruise terminal are very close together.
You might be able to get a shuttle for $5 from the cruise terminal to the airport. A taxie is not much more.
Try
http://boards.cruisecritic.com/ and look up cruise ports for info on the town.