What's the best place to have a picnic in Golden Gate Park?

Further west is generally less crowded, but further east is often warmer and less windy. Spreckels Lake is basically my backyard, so that's where we go most, but sometimes, it can be briskly windy. If you don't mind a bit of a walk up, Strawberry Hill in the middle of Stow Lake is lovely. It can sometimes be quite crowded on weekends, the various lawns at the San Francisco Botanical Garden at Strybing Arboretum are among my favorite spots. It's beautiful, and you can walk around and explore the garden afterward on the twisty, private paths.

http://www.sfgate.com/neighborhoods/sf/goldengatepark/ by Lloyd Lake. (Scroll down.)

generally the further west you go the less crowded it is. head out towards the bison paddock area, there are some lovely random fields :)

Also, I don't mind some people walking around us if it's a really really beautiful spot.

I had a nice picnic near I think middle lake near the bison paddock.

Spreckels Lake is nice. East or west side of the park, though, it's going to be crowded all over on the weekend. Plan your picnic for a weekday and you'll have lots of the park to yourselves.

Though http://www.sanfranciscodays.com/golden-gate-west/#marx isn't off the beaten path, I've been to lots of nice picnics there. For more seclusion - and more "interesting" than "lovely", try the http://www.sanfranciscodays.com/golden-gate-east/#horseshoe.