Bikes are particularly recommended if you want to go see the monuments. The monuments are somewhat dispersed, and since 9/11 they've made a lot of the area off-limits to cars. Unless we're at code Orange, you can ride your bike right up to the White House, but you can't get close in a car, and even if you could there's no place to park. The Lincoln Memorial is undergoing construction that makes it tough to approach by bike, you have to come in from the south side. The main avenues around the monuments, Constitution and Independece, are major commuting routes, but there are a lot of fun smaller streets around there -- Madison, Jefferson, and Ohio Drive come to mind. At this time of year there are a lot of, ahem, tourists around, and they tend to wander in front of bicycles, so look out.

In terms of crime, any place that is under the jurisdiction of the Federal Government is very safe, i.e. National Park Service areas. In the current environment you're probably more likely to get sent to Guantanamo than mugged. The rest of the city has it's danger spots, although it's not nearly as bad as it was a decade ago when we were the murder capital of the USA. I would not leave a bike locked up outside overnight in most of the city.

WABA, the Washington Area Bicyclists Association, has good information at their site, www.waba.org. Another good site is Bike Washington, www.bikewashington.org.