On foot
Given that the area is centrally located downtown, it is extremely accessible on foot. From the SoMa area walk northbound on anywhere from Fifth St to 11th St. Market St forms its broad southern boundary and makes the area easily accessible from either the east Union Square-Financial District or west The Castro, and from the north Nob Hill-Russian Hill it's just a 10-20 minute walk directly due south.
By Cable Car
One or other of two cable car lines — either the Powell/Mason cable car line or the Powell/Hyde cable car line (http://www.sfcablecar.com...) — can take you from Fisherman's Wharf, Chinatown, Nob Hill, or Russian Hill to the intersection of Market St and Powell St in Union Square — near the Powell/Market BART and Muni station. From here it's just one block to the Tenderloin.
By Muni
The neighborhood is well-served by public transit, provided by MUNI (http://www.sfmta.com/cms/...) in the form of the Metro system, the F-Line streetcar and various bus lines. MUNI Metro lines J, K,L, M and N serve the Powell/Market and Civic Center/United Nations Plaza stations under Market St along with the BART line. The MUNI Metro also serves the Van Ness/Market station, which is part of the same subway tunnel but is not shared with BART.
The historic F streetcar line runs on Market St between Castro St and the Ferry Building where it turns north on The Embarcadero to Fisherman's Wharf, passing by both the Civic Center and the Tenderloin.
From the Caltrain station the #47 bus takes you to along the western border of the area Van Ness Ave to City Hall. Other MUNI bus lines serving the area are: 49 Van Ness, 9 San Bruno, 31 Balboa, 5 Fulton, 19 Polk, 21 Hayes and 38 Geary.
By Bart
BART (http://www.bart.gov/index.asp) runs under Market St with two stops in the area; both the Powell/Market and Civic Center/United Nations Plaza. Both BART stations will put you well within walking distance of any Tenderloin attraction; the latter is the most convenient BART stop for the Civic Center.
By car
Directions for driving to the Civic Center are marked on the freeways. Once inside the City limits, two main arteries serve the area — Van Ness Ave and Market St.
There are several garages, such as the Performing Arts Garage at Grove St and Gough St, an underground garage under the Civic Center Plaza entrance on McAllister St, open from 6AM to Midnight, or 24-hour valet parking at Opera Plaza on Turk St just off Van Ness Ave. Where the freeway was prior to 1989 earthquake between Grove St at Gough St and Turk St at Franklin St there are several smaller open air lots, which will charge about $10 for all day or $6 for an evening. Those lots are gradually being displaced by new construction. Street parking in the Tenderloin is extremely difficult to find, but parking garages are plentiful.