Go to Chinatown.
Eat at Dol Ho or Y Ben for excellent and cheap Dim Sum. They are both on Pacific, just up from Stockton Street. Dol Ho is smaller and seedier, Y Ben is like a big banquet hall. Lunch only.
Or, if you want the quintessential Chinatown dining experience, eat at that wonderful, cheap, cramped hole-in-the-wall called Sam Wo, on Washington up from Grant. Not a place for whiners or prima donnas.
Explore the alleys: Spofford Lane and Ross Alley, for example. You’ll hear the familiar clicking and shuffling of Mah Jong tiles. Visit the Tin How Temple in Waverly Place.
Explore the Chinese markets and groceries on Stockton St.
Visit Old St. Mary’s Church, the oldest church in San Francisco. Across the street to the south is St. Mary’s Park, which is home to an art-deco metal statue of Sun Yat Sen built in the 1930s.
Visit Portsmouth Square. Look for the old men playing Chinese Chess on the northeast corner of the square. Then cross the footbridge to the Holiday Inn building and check out the exhibit at the Chinese Culture Center.
Chinatown has surprises around every corner, even for those who grew up in Chinese society. The rule: the farther north you go, the less touristy it becomes. The father east and west from Grant Street, the less touristy it becomes. Between Bush St. and California St., the only things worth seeing are the Chinatown Gate at Bush & Grant and the Sun Yat Sen statue in St. Mary’s Park.
Afterwards, go check out City Lights Bookstore and then have a coffee at Caffe Trieste in Little Italy. Both are on the northern periphery of Chinatown.