Rent a bike for the day and they'll give you maps with different routes through the city. Their bikes come with helmets and other safety gear, and their map of things to see by bike in the city is great...even if you can find a cheaper bike somewhere else check out their map.
Standard bikes run about $30 a day.
Their great map:
http://www.blazingsaddles.com/assets/blazingsaddlesmap.pdf
