Depends on what you're comfortable with. I commuted downtown for years, and never had problems - Ankeny to Burnside and up 3rd, and you're golden. Broadway or further north and it's slightly trickier just because you have to navigate the general area of the Rose Quarter, but still doable. The only part of town I really fear to go is Lake O - every time I'm down there, if a driver doesn't take a shot at me, it's a pedestrian or bad infrastructure.
That said, a few months on crutches will definitely make one more trepidacious.