You are doing great! Give yourself time and bike, bike, bike and you will improve. I have many hills here and they are a pain! I thought I could make up the MPH going downhill, but haven't found this to be true. I have managed to increase my mph on the same route from 10 mph to 14 mph in two years of riding.

What helped me besides more time on the bike was the free website called bikejournal.com. This site enables you to customize a journal for yourself where you can keep track of such things as goals, distance, average mph, date of ride, description of route, calories, etc. Over time, you can see improvement and I am sure you will. The ladies on this site and bikejournal.com are the best motivaters for fun, exercise, and improvement I have found.