I used to take trips out to see returning salmon for one of the local environmental groups, and I am not a big fan of taking folks to see them in places that are heavily modified, like hatcheries, dams, and the like. I have tended to take them to see salmon doing normal salmon behavior.
The best salmon viewing is from mid-October to early January. In the Redmond area, the local goverments will set up salmon viewing stations at areas along Bear Creek.
Another favored area is in the Landsberg area, downstream of the parking area along the Cedar River at the old railroad bridge. At Flaming Geyser State Park, it is also possible to see fish from the bridge on the State Park property.