I was in Nassau on my December cruise. Here's my thoughts--
I don't believe that Paradise Island is really within walking distance. If it is, it's a long walk. You can get a ferry right near the port for $6.00 pp round trip. Pay at the counter inside the shop area. I wouldn't realy trust too many people walking around outside. It is a nice ride across the water. Senor Frog's is a great place to go. It's within walking distance from the port. You can actually see it from the ship. It's on the other side of the straw market. Be sure to try the Conch Fritters. If you do go over to Paradise Island, Cabbage Beach is within walking distance of the ferry dock and the Atlantis Resort. I didn't go to Cable Beach, so I'm not sure how far it is.
We stayed at the Radisson-Cable Beach. It's approx. 5 miles. All you have to do is catch the #10 bus which is across from the Straw Market and it wil take you there. It costs around .50 pp and you need to have exact change. They won't give you change back.