some route possibilities for you between the N and #6. if you take the 6 you will travel above ground and go through the haight and through the UCSF campus then into the Inner Sunset (main intersection 9th and irving. you would get off at 9th and judah. you could explore here and then walk to the Grandview Park). the bus will now start to make a climb. in the Sunset the streets are alphabetical and numeric in a grid, easy peasy, except where you will be heading. get off at moraga street (J, K ,L, Moraga - at the ballet school). head west. these are short blocks. it will all be flat and then you go up some stairs, stairs and stairs to go up to GP. enjoy view, then come down the other set of stairs, cross street, go down stairs, turn around and see magnificent tiles. you can then go north on 16th to the N judah. if you want to get to GG Bridge, then head to 19th Ave.
now, if you like. you could take the N, that travels underground and alongside the UCSF campus and into the main area of IS, after this, they stop at about every 2 blocks. get off at 16th Ave and walk up/south on it. the street will incline and then you will climb about 100 steps. then walk flat for 2 blocks. then do tile stairs and GP. if you want to head to IS, it's all down here from here. if you want the nearest N - Funston (13th Ave.) and Judah, head east from GP, down stairs, cross street, down stairs then left on Funston. if you'd like to see the IS continue to Irving Street. you may want to continue into Golden Gate Park.
depending how fit you are and if you'll be sore from biking the GGB may determine what day you do this. There are no public restrooms for your excursion. you will need to purchase something at an eatery in IS to have access to a toilet. make sure you ask first if they have a toilet you can use before purchase!
oh, if it's sunny and hot downtown and you come in summer, you may want to bring a jacket as it's common to have 50 degrees with fog in the Sunset.