Would I be able to take buses all throughout New Zealand, or will I have to rent a car?

I plan on starting in Auckland and working my way down to the South Island. I was hoping I could just take buses throughout my journey to save money. But I don't know if buses run all over NZ. Also....I've never drove on the other side of the road before. I think ME driving a car that's not mine, on the other side of the road, in a country I've never been in before would be a disaster waiting to happen. Thanks for any help you guys can give me!!!!

Yes - there is many bus services throughout NZ - although the "Kiwi Experience" is the most popular and been around forever!

Its a New Zealand backpackers adventure travel network. Bus travel passes. Fun, freedom, fantastic value! You can even hop on and off as much as you want.

See the website for all the different options available. There's even 30% discount at the moment!

Another option is http://www.magicbus.co.nz

Yay man, you make sense in not wanting to drive if you are unfamiliar with our style of driving.
Buses will get you everywhere (almost)
Google names like:
Intercity, Newmans, Magic, Kiwi Experience, Naked, Southern Link, Atomic, Guthries, Bottom, Stage Coach, Citibus, Newtons, De Luxe, AAT Kings, Fullers, and they'll be heaps of others as well.
Probably best to go to the official NZ Tourism site.

I'd say rent a car regardless. I did it and its not that bad. I had never driven on the "other side" of the road either, but you get used to it really quick...and its pretty cheap too(like 15 bucks a day in the off season). We rented one down in the south island and it was perfect! We looped the entire island - it was the coolest! We got to see SOOOO much more that way!! I did get a ticket though...cause you drive through lots of little towns and the speed limit drops fast - so if you do rent a car watch out for small town kiwi cops! (: Seriously though...I promise, its not as bad as you think...the worst thing about it was the blinker is on the other side of the steering wheel, so I kept turning on my windsheild wipers instead of the blinker (: Again though - you get used to it real fast and it give you awesome freedom to stop when you want to and take in the incredible scenery you are go to see!! There are buses...but rent a car...I promise you will not regret it and you will be so happy you did!!

HAVE FUN!!! New Zealand is amazing!!!

Kiwi Experience is readily available but I woulod not recommend.... Have family in the tourist industry and I don't like what I hear about their accident record.

Intercity buses cover the country and another option is The maked Bus Company, not sure of web site but you'll find it on google. Depending on bookings their tickets can be as low as $1.00!!! cheap travelling