... would ride the public roads in New Zealand. They are narrow, often have no shoulders and, worst of all, car drivers simply don't give a damn.
My advice (as a long-time, long distance worldwide touring bicyclist who has [foolishly] ridden everywhere in New Zealand): kit out your mountain bike for touring and ride some of the thousands of miles of unpaved farm, park and forestry roads. Take public transport (buses) between locations. Of course you won't be able to ride genuine single-track or bushwhack with panniers nevertheless you can have a great trip never having to worry about that car coming from behind.
(I have no comment to make about this Lonely Planet title.)
PS. No complaints about the helmet law, please. It's the price you pay for having *free* accident coverage if you happen to cracka you coconut. Without asking any questions they cart you off to the hospital and give you whatever you require, whether it's a band-aid or brane surgery.
PPS. Bring your lowest cog set. We do hills here; rarely long but always, always steep.
PPPS. There is no safe way to cycle through Auckland, and getting to or from the airport is a nightmare. Even weekends are bad. Nevertheless, it is possible to bypass the worst of the city traffic: do a Google search for "Manukau Harbour water taxi", email/phone the proprietors and arrange the water taxi between Clarks Beach (southwest of the city, nevertheless an impossible ride from the airport) and West Auckland. A road map will then direct you toward State Highway 16 to the north. Vice versa if you are heading south. It ain't cheap but you will still be alive.
Review redux (August 2011): I now see the water taxi has gone down the gurgler (the business, not the boat.) You're on your bloody own, mate, and good luck to you. They're working on a bike corridor through Auckland but it's slow going; from time to time you get pitched into dense traffic; no fun.