Visiting USA for 1 month, best prepaid plans?

Hello all.

I'm visiting the USA next week for a month to see my family and will be going to Michigan, Kentucky and California. I need data and voice during my stay, especially in Michigan where I will be staying with older relatives who don't have the internet.

I am from Australia and here you can go to any phone store or even the supermarket to buy a prepaid sim card, which you can put into any phone, and you can "top up" with more money when it runs out, but you can never spend more than you have on the card.

I have used this site to find what carriers use 3G bands supported by my phone (HTC Desire HD) in the areas that I'll be visiting and have found AT&T and T-Mobile to look the best. But I am confused by AT&T's $50 Go Phone plan, it says it is unlimited voice and data, which sounds great, but then it says you need to sign up for a separate data plan, which all seem to have limits. In Australia anyway there are a lot of weasel words when it comes to mobile plans, like 'unlimited' not really being unlimited, or a 'cap' not really being a spending cap. It also seems like you can't just get a sim card by itself, you have to buy it with the phone.

So I'm looking for some help understanding how prepaid works in the USA, and which plan would be best for me to be able to use with my existing phone. I know some of this will probably sound pretty obvious to a lot of you but I know that a lot of basic assumptions you might make about how the mobile system in some country are likely to be wrong, such as in the USA you are charged for both inbound and outbound calls, whereas a typical Australian would find being charged for.inbound calls pretty ridiculous.

 

Thanks for letting me know about Cricket, but I think I want GSM as well as 3G since I might be in some remote areas at times.

Has anyone tried the AT&T Go Phone plan?