We're going to San Fran but only for a few days, where and what should we see within that short space of time?

for culture, try SFMOMA (museum of modern art), SF Opera (among the world's best), chinatown, north beach and the mission district. for history, there's alcatraz, the coit tower on telegraph hill, ghirardelli square (if you don't mind commercialism), and, for more recent history, city lights bookstore in north beach and the haight-ashbury which was front and center during the late 60s and early 70s counterculture era.