My mom once lived in a commune on Liberty Street, back in the 1970s, and so I went there (having forgotten the specific address) to just look at the many Late Victorian houses and tromp the hills with my baby in tow. There are several great staircases bordered by lush plants, so leave the stroller behind.
Liberty runs for just a handful of blocks, running parallel and between 20th and 21st Streets, to the north and south, and perpendicularly hemmed in between Castro and Valencia, to the west and east.
You'll traverse hills, navigate stairways, and see some beautiful views. Sustenance and bathrooms are only blocks away--south to Noe Valley, west to the Castro, and east to the Mission neighborhood.
Stairways not to miss:
--Sanchez to Liberty Street
--Liberty Street between Noe and Rayburn Streets
And if you want to have fun on the STEEPEST STAIRS in the City, deviate your path off Liberty and go to Sanchez and 21st. :-)