We prefer the WDW transport system. Not only for the comvenience, we meet the nicest people while on the bus! It is just part of the Disney magic for us! Some of the bus drivers have hilarious and informative spiels while they drive.
I have not been to many beaches in Florida, but I do prefer the Gulf side. My favorite beach of the ones I have visited is Siesta Key near Sarasota. This may be a little far for your stay in Orlando.