Consumer Reports rates the Fit near the top of the subcompacts for both for the manual (Fit Sport MT, 33 MPG) and automatic (Fit Base AT, 30 MPG). The Yaris is rated more in the middle, but it looks like it costs about $2K less. They also like the Nissan Versa in both sedan and hatchback, but the mileage is a bit lower.
For a slightly bigger car, still with good mileage and not much more expensive, they like the Hyundai Elantra (auto, 29 MPG), Toyota Corolla (auto, 32 MPG), Kia Forte EX 2.0 (auto, 28 MPG), and Mazda 3 AT (auto, 28 MPG). For a manual they like Mazda 3 MT (30 MPG) and Toyota Corolla Base (32 MPG).
If you can live with a diesel, the Volkswagen Golf TDI is top rated and it gets 38 MPG.
Of course, you can spend some more and get the larger Toyota Prius with even better mileage. CR has always rated it highly and they reported on a 10 year old car saying it still performed well.
My last rip to Silly Putty Valley scored me a Kia Soul, I went back to the rental desk and immediately insisted on a different car. I'm 6' 3" and 250 Lbs, I don't fit in compact cars, cattle class airline seats, or the hotel version of a twin bed. After being told that was the only car they had left I reluctantly went back to the car and found that not only was there plenty of room behind the wheel, this rental turned out to be a pretty zippy little econo-box! Not much room for extra stuff and it would be hard to get four Otis sized folk in to one of these cars but still not a bad car for short trips across town.
How would it perform at altitude? Would the grind going up an down the hills be too much for it? How about bad weather? Could this car hack it in the snow? I dunno.
I can explain it to you but I can't understand it for you.
"Any man who thinks he can be happy and prosperous by letting the Government take care of him; better take a closer look at the American Indian." - Henry Ford
Corruptissima re publica plurimae leges; When the Republic is at its most corrupt the laws are most numerous. - Publius Cornelius Tacitus