Well, As Fred said this is a good question. I'd be willing to bet that you'll get lots of feedback.
This is my recomendation book a 1 day guided trip with John Hazel on the Deschutes river in Early to Mid October, then spend the rest of the week fishing the Deschutes on your own.
This is assuming you are at least moderatly healthy and the thought of wading in some reletively powerful currects is ok. (not suggesting anything unsafe is necessary, just that it's a big river and some slots have some current. The Deschutes in October is about as about as close as you can get to a sure thing. If you spent a week there i'd guess that hooking 10 Steelhead is VERY likely and the potential for hooking substantially more than that exsists.
Also you should know that October is a time of plenty in the Northwest. Every river that has summer steelhead will be in it's prime time. So you could spend a few days on the Deschutes then go exploring.
Feel free to ask more questions!! thats why we all come here to share information and learn
Only steelhead matter!