first of all, I've been in your shoes.

if your trip is planned for a set date in late october....bring a rain coat and hope for the best. if the river looks fishable that time of year its generally safe to float, especially if you stick to the lower end.

another good clue is whether or not you are the only guy at the put in. I've been that guy, wondering why my float was so short, then getting home to see that the river had risen 4000 cfs in two hours on me.

best thing to do is bring the whole kit and caboodle. be prepared to fish everything else, including smaller lesser known tribs from the bank if conditions keep you off the hoh, which to be frank is as likely as anything else to be the case.

your just as likely to have as much if not more success on some of the rivers around anyway.

the hoh is class 1 water all the way so you shouldn't be able to get in too much trouble if you have some experience on the oars.

avoid the known trouble spots (oxbow, the park float) until you've either watched, ridden with or followed someone who knows the trick.

other than that, if it looks good, go for it.