Murray Bridge has a great selection of bike trails, travelling either along the river, or inland. Choose from beginner, intermediate and advanced routes. A great one to try is the Murray Bridge to Monarto trail. All of the trails are well sign posted.
If vast water views are your thing, then try cycling from Meningie, around Lake Albert to Raukkan. Here you can visit the Point Malcolm lighthouse, Australia's only inland lighthouse. The views from Raukkan are sensational, and the community is very welcoming.
The Tailem Bend Community Centre has free bike hire - take a cruise along the river clifftops and stop at the Riverside Hotel for a lunch with spectacular river views.