My WRX has about 1700 miles on it and I don't think that the fuel mileage is that good. I do push it pretty hard about 50% of the time but I'm only getting about 18 to 19 mpg. Does this sound normal?

That is probably normal if your shifting at high RPM’s . When I first got the car I fooled around a bit and ended up with mileage like that on the first fill up. After that I settled down and now get 26 MPG consistently. There were a couple of previous threads on this topic and it sounded to me like 24 or 25 MPH were the most common.

I have found that by avoiding high revs while shifting (max usually below 4,000 RPM) I get from 25 - 27 MPG. This is achieved in mostly highway driving.