In theory you can, but it may depend on some restrictions. I have an Australian version and we don't have the option to switch between km and miles - the menu option is just not there, but on some models (Euro or UK I think) there's another menu so you can choose miles or km, and then the fuel consumption units. We just get L/100km, but if your speedo reads in miles you can choose mpg or miles/L (!) for fuel consumption.
Not sure if miles means UK or US though, which would definitely be something you should know.
1 UK gallon = 4.546L
1 US gallon = 3.785L
You can change the Aussie mileage readings: Owners Manual page 38-43 (Instruments - Display settings) you run through; Clock, Background Brightness, HISS Indicator, Speed & Mileage, Fuel Mileage, Subtraction Trip. You can select Ks or Ms, & then change fuel mileage. (if you have selected Miles, you can select MPG or miles/L).
I would think that most ATs would have this option.