October could be a lot of fun. The leaves would all be gone from the trees and the rivers should all be small, clear trickles (maybe even partially frozen over) by then. NO bugs, and the vegetation will probably all be frozen and down. Weather could vary dramatically depending on which geographic location you intended on, and whether you intent on going to the alpine, or stick to the valleys. If you are going to Denali, you should count on snow and near-zero (Farenheit) temps at night. Here in the Chugach, or Kenai Mtns it could be mild, ie mid-20's at night, some rain, some snow. However, it could be downright nasty that time of year here in South-Central.
Personally, that time of year I would choose some closer-to-civilization (Anchorage) overnighters or extended weekend type trips in the Chugach or Kenai range. There are more established trails and routes, and you can always bail out if the weather decides to get real bad. Not an option if you are several days back in Denali and it decides to snow several feet and drop to sub-zero temps. And then it could stay that way ALL year.
October is probably the most HIGHLY variable weather month up here, so you would need to be prepared for the worst. This is not meant to discourage you from your game plan, but to provide my (possibly subjective and mostly accurate ;-)) opinion on what to expect that time of year. I really should get back to work now!