WELCOME to the DIS mar2728!
Bus, boat or monorail transportation are part of being a guest at a WDW resort so yes you can use it whether you use your theme park ticket or not that day!
To get to dinner at another resort what you'll have to do is hop a bus to one of the parks or DTD.There will be buses for all the resorts at these areas.Hop on the one you need.
>>>Please allow plenty of time though. It can easil;y take you 30-60 minutes to get from one resort to another for supper. Our last trip, it took 45 minutes to go from CBR to WL for supper. We didn;t mind though, supper at the Whispering Canyon Cafe was fun then we took the boat to the MK.