Getting around in the United States is sometimes not very easy. Most people own their own cars, but not everyone can foot the bill for the car, plus the insurance, gas, and maintenance. Most big cities have buses, but they are much slower than a car. Several cities in the U.S. have subway systems, but many do not. There are even fewer trains that transport daily commuters. In cities such as Los Angeles, public transportation is much more limited than in other countries.
If you take some form of public transportation, you need to pay a certain fare. In most big cities the fare is anywhere from 1 to 2 dollars. But don't expect the bus driver to change a bill for you. You usually need exact change if you're going to ride a bus, train, or subway. Whatever you take, you always have to pay for it!
My friends here in Los Angeles all have different ways of getting to work. One friend, who lives out in the boonies, rides the train everyday. He takes the train because it's easier for him than driving or taking a bus. Another friend I know who works close to where he lives rides a bike everyday. Still another friend drives his car. I don't know anyone who rides the bus, but I've taken it once or twice when my car was in the shop. Worse comes to worst, you can always hop in a taxi. Taking a taxi is expensive here, though, so be prepared for a big fare, not including the tip!