I did it in September, during a really warm summer, and water was scarce. I would imagine October would be even drier? I'd bring 3 bottles.
Regarding bears, just assume they're everywhere, cause they prob will be. I think I saw a dozen unique bears, each one at least a dozen times. The berries were ripe. They were almost as common as goats. The goats, btw, are SOBs.
Other than water, I think the only other challenge would be coming down the elwha snow finger. it was pretty rotten already when I did it in Sept. so I imagine if any of it is left, it's pretty unstable. You do NOT want to fall through that thing into the river below.