Yeah, that part was confusing to me. He's going to SF and you're having the party in LA? We're like Texas out in Calif, big distances.
My suggestions are to go down to Ocean Beach at the west end of the city, take a walk and watch those breakers coming from all the way across the Pacific.
Cross the Golden Gate bridge and go out to the headlands for great views, in September you will have the best weather of the year, warm and a lot less fog. If there is fog, it will burn off by noon in Sept.
Take a ferry across the bay to Sausalito and have lunch and walk around. When you go down to take the ferry, walk around near the Ferry building, go to the farmer's market, have a nice breakfast.
Walk around in Chinatown, go in stores, have some dim sum.
Go to Golden Gate park and go to the Japanese tea gardens and see the koi and the lilies.
Skip Fishermans' Wharf, waste of time and money. The Alcatraz tour can be fun, it's touristy and all but if you don't get to take the ferry to Sausalito then you'd at least get a short ride on the bay. Personally, I think taking the Sausalito ferry is more interesting and it's a lot cheaper. Well, it's cheaper before you buy lunch and shop