Haven't visited yet but am planning to visit in future. Most people head to Siam Reap and phnom penh.... And I heard that USD is widely accepted there. You probably shouldn't and can't change to the local currency.
Cambodia is a very up and coming,and still very cheap wont need an inerpreter you can always get by in english all over south east asia. Ankor wat is stunning and the killing fields are a must when out there, some of the beach places are worth a visit vey much like Thailand with less crowds Kep and sihanoukville comr highly recommended, the food is amazing also kind of a cross between Thai and Vietnamese. Enjoy