Man that would suck. Quiet hostels occupied only by foreigners are awesome.
Which town? I've stayed in hostels before and thankfully never encountered an Australian bogan/feral. Generally find travellers to be a better kind if people. I'm doing 10 weeks backpacking through NZ over Christmas/New Years before I hit the US/Canada for about a year, can't wait.
I'm in a place called Kaikora at the moment. It's on the South island about 200km North of Christchurch. Really recommend coming through here for a few mid week nights when you come over. Probably wouldn't stay for a weekend, but given you're here for 10 weeks you have enough time to sacrifice a weekend or two in a quite town along the journey. In saying that, it wouldn't surprise me at all if this place got quite lively on a weekend during January and February. There is about 7 backpacker hostels within about a square kilometre so I imagine there is enough demand in summer to cater for them.
Tiny town but there are a handful of bars which I plan on frequenting one or two tonight. But there's loads of stuff like walks, kayaking, whale watching, dolphin swims to do. Unfortunately my budget has been blown to shreds so my wholesome activities need to revolve around cheap or free things so I'll just be doing a hike today.
My biggest piece of advice for you, delay getting to Queenstown as long as you can. So many travellers I know have come to NZ for 2-3 months, get to Queenstown straight away and don't leave the place and don't do anything else they wanted too. Not even half an hour ago was chatting with an English lass who stayed in Queenstown for ten months of her twelve month visa and hardly saw anything else of NZ. It's a seriously awesome town, but so addicting. Definitely go to Queenstown, but get everything else out of the way first.
Wellington (south of the North island) is a great city for nightlife and gigs. I'm giving high consideration to moving there for a few months in January. One of my favourite cities on the planet. In Picton, Nelson and Abel Tasman (north of the South island) there is a big national park with loads of stuff to do. There is a four-five day hike through Malborough Sound (Picton) which looks really cool.
Not a fan of Auckland and I've only met a few people who like it. Don't ditch it completely on my advice but don't expect much of it. I don't know anything between Auckland and Wellington. Lake Taupo is supposed to be real nice, and same with Rotorua but the latter is more of a coupley thing.
Would give consideration buying a car for about $1000 and selling it when you leave.
It's such a good country. I'm so dumb taking till 25 (2009) before making my first trip across the ditch. Been back half a dozen times since.
Lets face it, the only reason most Aussies go overseas is to get drunk. That's always bound to ruffle the native's feathers.
It's not just going out getting drunk. I spend a lot my travelling time in bars, getting drunk, but I don't act any differently to how I would back home. For some reason so many of our countrymen see being overseas as an excuse for acting belligerent whilst on the piss and doing stuff they wouldn't do back in their home towns. I can see why they do it, but it's still stupid and you won't see many Germans, Spanish or Dutch deciding to go apeshit because they are out of the home country.