Riding a bicycle offers so many other benefits beyond those related to your health (which alone should be reason enough). You can navigate the city faster, safer, leave less of a carbon footprint, save money and perhaps you might even notice some things you would never see in your car with your music blasting.
If you don't have a bike in the city but would like to start commuting, Capitol Bike Share is a great program. For $75 a year you have unlimited access to a large population of bicycles which allows you to get from place to place with ease and enjoyment. I am almost certain you would spend at least $75 a year on your own bike between normal wear and tear.
Long story short... Start biking, it's good for you.