Flying into Medford & back to Portland on the return will add about $100 to your air fare, but.....
For starters, there are a hell of a lot less people & traffic to contend with than the Portland area.
The top end of the Rogue is about a 30 mile drive from the airport, the lower end about 50 miles the other way. You can get a nice motel in town or stay at a nice motel right on the river in Shady Cove. There is a flies only (not fly fishing, but no bait or lures) season on a section of the Rogue during September & October. Being as how that coincides with Elk season, that thins the crowd down considerably. There are several of us local guys who can show you around. Plenty of guides to choose from. Check the fly shop in Ashland.
If you want to see redwoods, highly recommended, drive from Medford over to Brookings on the coast. Swing down into California & Jededia Smith State Park. Be sure to drive down thru the Avenue of the Giants. Take a camera. Your buds back home won't believe the trees! You have the Smith river just over the border in No Ca. In fact you'll drive along a section of the Smith before you come into Brookings. The Smith gets some big winter steelhead. It is actually as famous, if not more so, than the N. Umpqua, but being on California's Lost Coast
, further from any major metro areas, it doesn't get the attention the N.U. does. If the Chetco is still open, that's another option, right there in Brookings. The mouth of the Rogue is right up the road at Gold Beach. You could easily spend a whole week over there on the coast.
The Umpqua is about a 100 mile drive up the interstate from Medford. The fly water on the North Umpqua is easy enough to get to but the accomodatiions in the area are rather sparse. Outside the Steamboat Inn, which is quite nice, it's slim pickings. I'll let others, more knowledgeable on the N Umpqua, fill you in on that option.
As far as I'm concerned, the Smith beats the Klamath any day, but I won't argue with anyone who thinks otherwise. A lot of Oregonian's run down there for day trips.
To my knowledge, the Deschutes does not have a winter run of Steelhead or Salmon. But again, I'll let others comment on that.