Wich wireless plan should I choose for my Iphone 4s??

[rhcp76]

Hi,
I am from Canada and I have a unlocked 64gb Iphone 4s.
I travel often in the United States and I would like a U.S plan for my Iphone. I often go in Florida and it is for 1 month each time.
Is there a company that sell SIM card for my Iphone with monthly no contract plan?
Thanks