Adjoining the windy bay on the sunny side of town, San Francisco's downtown (officially "Financial District") provides unusual visual expansiveness and fresh air in a hyper-urban locale.
With a lot to see (including the iconic Transamerica building) and a surprising amount to do - the Embarcadero and/or Yerba Buena Gardens provide good starting points.
Eating options are plentiful, mundane and tend to be expensive - demand surpasses supply. Red's Java House is a fun bay-side exception to this rule (although a ways from Market St). The nearby Union Square area provides much of the city's best high-end shopping, and North Beach and Chinatown are also within easy walking distance.
MUNI and BART also provide faster and cheaper transportation options than driving. Bike lanes have been added to Market St, in addition to the ones 2/3 blocks south on Howard/Folsom.
Wikipedia: http://en.wikipedia.org/wiki/Financial_District,_San_Francisco,_California
