Boulder Creek Path is a pretty good place for a stroll. One good point about it is that if you're not up to walking the whole path, there are ample places to park and just walk a short stretch.
Boulder Creek is a pretty creek wherever you pick to walk it. There are a couple of places where you can stand below the water level and look through glass, sometimes to see the occasional visiting trout.
One caveat: keep your eyes and ears open for bicyclists--some of them zip right past you, and not all of them advise you that they are coming.