Travelling to the USA and need some help

Hi,

I hope someone can help me.  I have an unlocked iPhone 5 and am travelling to Florida in the next few months from the UK.

I wanted to get a T Mobile Nano Sim Card and then get the Monthly 4G Prepaid plan Unlimited Web and Text with 100 Minutes talk for $30.00 just for one month.

Is this possible to do with no contract as I will not be staying for longer than one month in Florida before returning to the UK?

If so how do I go about getting a nano sim card?  Can I go to a T Mobile store in Orlando when I arrive and do this, could it be done same day?

Any help would be much appreciated. 

Thank you.