We have just got back from Orlando and went through 3 prepaid phone cards. Make sure you read the back of the phone cards especailly if you are trying to contact your bank. Once of my cards ( Pench Penny) would not expect the 0845 number and i ended up using my uk mobile - cost a fortune!!!!!!

When re-charging your card you will have use your credit card or a US bank card if you have one.
Hope that helps
[8D]