You can get just about anywhere in Los Angeles by public transportation, but it’s a very slow and complex system unless you’re on a direct Metro route.
The best website for planning your route on public transportation is socaltransport.org, which incorporates the Metro system and multiple other systems (but not LADOT at this writing).
The Metro subway (not all routes are underground) system is still growing. It currently has four lines. The Green Line goes east from near LAX connecting with the Blue Line in central LA and on to Norwalk. The Blue Line runs from Long Beach to Downtown LA and the Red Line. The Red Line runs from Union Station through downtown and up through Hollywood to North Hollywood. The Gold Line runs from Union Station northeast to Pasadena. Metro buses extend routes from Metro stations to areas not reached by the trains.
Read about How to Ride the LA Metro.
LADOT (Los Angeles Department of Transportation) offers bus service within the city of Los Angeles and connects to the bus systems of surrounding cities and to Metro buses. LADOT runs the DASH system, the Commuter Express, the San Pedro Trolley and the Hollywood Trolley systems as well as City Hall and Metrolink shuttles Downtown.
Santa Monica’s Big Blue Bus system serves the Santa Monica and Venice area with lines extending to adjacent cities.
Long Beach Transit serves the Greater Long Beach area and includes the Aquabus and Aqualink boat services between waterfront attractions during the summer and weekends the rest of the year. The free purple Pine Avenue Link runs along Pine Avenue from Eighth Street to Ocean and connects to the Aquabus and Aqualink. The red Passport busses are free within the downtown area and to the Queen Mary, but require a fee to Belmont Shore.
For a complete list of local transit websites, click here.