The river between ZFalls and Hammond is a great area to work. As for parking/walking I can’t help much but the gravel road that follows the river isn’t all the busy for a quick stop and a few casts when the river is along side the road.
SE Minnesota is full of fishing opportunities along the Mississippi River. The dike road between Wabasha and Nelson, WI has several good areas you can just park and walk to. Lake City and Red Wing both have great shore fishing right in town. I’d go with Lake City and fish either the big concrete pier or the breakwater. Wabasha Marina will offer some fishing too when the boats have been pulled.