Cairns is a nice town and the climate in October is pretty sweet (about 30 degrees with a cooling wind, but can be quite cloudy). There's everything you'll need here as a backpacker, but you soon feel the need to move on. I have spent 9 days here, but did a 5 day open water scuba diving course, and i'm itching to get moving.

Nightlife is pretty good.

I stayed in the Calypso Inn, which is fine but 20 minutes walk out of town.

There's no beach, but a nice lagoon.

Definitely visit the Great Barrier reef, either to scuba, intro dive or get you open water licence (live aboard boat trips are great!)