I'm going to Florida, but I thought that most major stores would all over
the US.
I can't do mail order, they won't accept a non-US credit card.
If you're shipping locally to a US location, just use paypal or one of its
variants to "launder" your foreign credit card into US funds.

)
If that doesn't work, you can buy Visa and Mastercard "debit" cards at
some stores. They come in some minimum denomination but you can add more
money to the account when you buy the card or can recharge it later at
approved stores. They're used just like a credit card and can be used for
online orders but be careful because they're debit cards, not credit
cards. If something isn't as advertised, you don't have the same consumer
protections as with a credit card. The same is true of paypal.
I'm pretty sure Circuit City carries them. It seems likely that stores
like Target and Wal-mart would have them, too. I'm not sure but I think
you have to provide an address to activate them, and for online orders
this probably has to match your local shipping address.