Currency is US dollars. Travellers can easily exchange currency and cash traveller's cheques at banks across Orlando. You can also withdraw dollars, though usually there is a small charge.
From the UK dial +1 for the USA. The code for Orlando is 407
In most cases UK citizens will not need to apply for a visa before travelling to Orlando. So long as your visit is for holiday or business and is not longer than 90 days you should be able to enter the USA under Visa Waiver scheme. Though you must apply for your ESTA before you'll be allowed onto your flight. Click here to apply online.