My commute is very much in the city - lots of stop and go, hardly get above 40 for more than 30 seconds
Don't get discouraged. Also note that some comments on this thread are not on TCH's. City driving should yield high mpg's averages. However, if you're getting up to 40 miles per hour in short distances then you're running your ICE a lot and not going to see high city milages. I'm not sure what you drove before the TCH but what kind of milage did you get there? Anything near the EPA? All things are relative. If you could get up to speed and let off the gas then use the battery to power you the mpg's will increase. However in traffic you may be intimidated to jack-rabbit start and not want to appear to be a slow driver. Traffic would move better with a smoother flow if everybody didn't jump at the light , fly to 40 and then slam on the brakes at the next light.

Then again I don't know that you can change people. You do however have the right (reguardless of the middle fingers flying) to obey the traffic laws if you so desire. Hopefully with some practice and patience you'll do better. One thing for sure though when everyone is sitting at the light and your ICE is not running you're still doing a lot better than they are.