Some notes on MPG:
1) Cold engines deliberately run with more retarded ignition timing to heat up the ctalytic converter as quickly as possible. A lot of short trips with long gaps between them will thus skew the average mileage to the low side. On the same note, letting your vehicle warm up in the driveway is also very inefficent, partly for the same reason.
2) I have found that efficiency is much less about how hard you accelerate up to speed than how long you wait to let off the gas. I have tested this with multiple vehicles by isolating these variables (aggressive accel + max coasting, light accel + max coasting, aggressive accel + min coasting) and have seen far and way the biggest difference coming from what proportion of the trip I spend coasting. Hypermilers know that coasting is how you make up the most that energy used to accelerate the vehicle. Try letting off the gas as early as is comfortable. Another way to think of it is to consciously minimize braking effort. I know this is a major constibutor to me breaking 20mpg in my 4Runner. In both my Honda Fit and Civic, I consistently show 42+ mpg in town when both are rated at around 30mpg city. My wife gets about 10% less than I do, all else being equal, simply because she isn't as meticulous about coasting.
3) Check your tire pressure. A lot of shops fill up to the standard 30 PSI, but that is actually too low for lots of vehicles. Depending on sidewall stiffness, they might require 35-40 or even higher. I have 150k miles between my Fit and Civic running max PSI, or even slightly above, averaging about 43-45mpg for both when I drive. On the previous set of tires on my Fit, there was a ~5mpg difference between 35psi and 45psi. Some folks like doing the chalk test to approximate the ideal street pressure for the tire stiffness and vehicle weight.
Also, indeed, high altitude and winter gas can't really be helped. Plus, it should get more efficient as it breaks in.
All that said, I get around 22-23mpg average when I commute in the 4runner, and the wife gets around 20-21.