Depends on so many things:i get now around 21mgp around town. Would that be normal? It's 100 degrees here in Texas so AC is a must.
How long are your trips?
Does your car sit out in the sun?
How bad is the start/stop traffic?
I have gotten low 20's in town for short 5 minute trips in the summer here in Phoenix. The AC can use a lot of power if it wants too.