Going to US from UK, looking for UK contract or US PAYG Help

[kAoTiX]

I am going to the US in a month and staying for just under a month, I will be taking my iPhone with me but I wanted some help on what I should do.

I need to have a phone in America and previously I've just purchased a $12 phone from Target and that did me fine. Is there any plans on o2 contract in the UK that are cheap enough to use in America? or is there a cheap enough PAYG sim I can pickup in America and put in my iPhone?

iPhone 3G 2.2 Jailbroken + yellowsn0w

Any help would be greatly appreciated.