Not exactly an answer, but more a commentary on my recent experiences acquiring a cell phone in the US - in MIA.

I have a Tri Band cell that I wanted to use in the USA, and my SIM card couldn't be used in the US so I needed to buy a SIM card.

It took me ages to find a place that :
1) Sold SIM cards seperately
2) Sold it at a reasonable price

I eventually had to pay $80 for the sim card and then $50 for the minimum initial credit.

I was somewhat ripped off, because they should have included the Initial Credit in the price of the SIM card, but because it wasn't stated, and I was sufficiently stupid to not actually have asked.

Also, In the KLM forum you might get an answer to this because KLM FD elite members get a free rental of a phone in the USA, but I cannot recall the exact details.