iPad 2 and micro sim question ?!?!

[Lilybee]

Dear all

My wonderful DB is purchasing an iPad 2 with 3G connection here in the UK. Now, I believe the iPad is unlocked so can take any sim card. I would like to know if my DB could purchase a PAYG sim card over in the US and just pay for when we need it ?

If he can. Who supplies the best network around Disney and how much does it cost to 'top up' ?

Thanks