As a tip, play with the public transit routing option on Google Maps.
Just use "Market St & Main St, San Francisco, CA" as your starting point. That is essentially on top of the Embarcadero BART station.
As an example,
here's a route to Chrissy Field (also Golden Gate Bridge and near Presidio).
ETA: Oh, and I should mention that the N doesn't actually go INTO Golden Gate Park, it runs parallel to it on Irving. You'd get off at 9th Ave and walk the couple blocks into the park (this would be near the museums).