San Francisco's Muni system can be scummy, inefficient, and scary, but I'd recommend any visitor take the bus vs. a cab at least a few times. Other than walking, riding the bus is the most entertaining and memorable mode of transportation. In a city with so much diversity and so much colorful scenery, every bus line offers a different experience. I met this guy on the 45 through Chinatown and he just made my week. You never know what kind of character you'll meet or weird things you'll see!