been a while since I did it but, you can get a usa card either from a US company shipped here or from a UK company, £30 ish unlimited 30 days, however I just went into the first phone shop I found leaving the airport and bought a sim card with calls and data PAYG, I was working there and needed one for 6 months but there were loads on offer.
Just be aware that it used to be the case that you paid to receive calls in the US so that came out of any call allowance, I think it has changed now but check if you get something that has limited minutes.
For a tech advanced country the telephone system is feck up or was as I say has been a few years, local calls from normal phones was fine but out of area constant request for who your long distance carrier was, the advantages of subscriber trunk dialling seemed to have passsed the USA by, in the end just used a mobile for everything it was way easier, it was a bit like going back to the 60's with a and b buttons in the telephone box very weird