We have been trying to time the coho run on the harrison for a few years now. I don't know about the springs (or if there is even an opening on the Harrison) I have been taking a week off each year to come down for coho fishing and the third week of October to the first week of November seems to be the best from what I hear.
We usually take the week after Thanksgiving off and fish the vedder, but have spent the last few years trying the Harrison side of the valley. Generally speaking, the week after thanksgiving has been really good on the vedder and there can be good days on the Harrison at this time as well. I hope this helps.
For me, if I lived there, I would simply be fishing the rivers as much as possible. My unlce always says "you can't catch a fish if your line's not in the water."