Since you already found Fuelly here's mine:
http://www.fuelly.com/car/scion/fr-s...tcaster/177974
Depends on the freeway, elevation changes, traffic and how aggressive I'm feeling. I can set the cruise control to 75, do some passing, zip around traffic, climb some hills and get 30 mpg all day long. I can set the cruise to 65 and poke along in the right hand lane and get ~34. I'd guess if you're comfortable cruising at 55 mph and drafting behind a semi-truck you could be comfortably in the high 30's.
Never forget that the onboard computer overestimates how good your fuel economy is, and go for a test drive this thing is miles different from a mass market sedan/coupe from Honda or Toyota in terms of comfort and practicality.
Edit: Don't forget to turn off the A/C when hypermiling, this car has little insulation so even at 'cool' the engine will still warm up the air in your face, might get another 1-2 mpg if I sweat it out but that's like $1-$2 per fillup at most.
Edit 2: My car is a manual transmission, the automatics get better economy but if you have any desire to get the manual than do it.
Just chugged through the math, assuming 25 mpg avg. vs. 28 mpg avg. and the MT being $1,100 cheaper than the AT you don't start saving money until you've driven 60,000 miles on the AT at $4.2/gallon.