dickytim: AT&T buy sim card then recharge card, $50 will get you 250 min talk, unlimited text to 100 countries and 1GB data.
Pay cash for both and you're away.
DO NOT tell them it is for an Iphone or Ipad if you can help it.
I went on T-Mobile for my Ipad4 for $35 for 3.5GB on "4G" which is actually our 3G speed.
The coverage was good most places, with the exception of a small patch on the coast from LA to San Fran.
In Anaheim there is a block of shops with a T-Mobile and AT&T store across the road from each other, when AT&T told me they wouldn't connect my Ipad I walked across the road and T-Mobile were more than happy, in fact they broke down a mobile Wi-Fi to take the sim card out as they had no other ones in store.
Definitely however pay cash in both instances and have your NZ ID there as well.
Thanks for the info.
I didn't realize T-Mobile would take cash (much prefer to pay like that if possible).
From what I've read, T-Mobile is solid option if you've got an iPhone 5 (not to so good for our 2nd phone - iPhone 4).
From David's story, sounds like AT&T don't like selling the (cheaper?) data plans if you have a higher-end smartphone. Then again, one wouldn't buy a decent data plan unless they had a smartphone in the first place anyway, or maybe it's certain a class of smartphone - like the iPhone 5?
Did they ask you specifically if it was for an iPhone/iPad (a specific model even?) or did you volunteer it?