I watched some review videos about prius. looks like you have to drive it very slowly.(like a grandma ).If you can drive it about 37-40kmph then you will get around 58 MPG. If you are going up in a hill you will loose you fuel efficiency. If you are coming down in a hill (gliding) you will save fuel.
Anyway prius fuel efficiency is very higher than its competitors. (like Honda Fit Hybrid). It comes with a lot of features. (I'm not sure we will be able to see them in sri lanka).
If you are willing to sacrifice your speed, then you will able to save fuel.