What makes this route worth doing now rather than in October: morning fog typically clears by 10am in late spring and early summer, leaving you with open Pacific views from the bunkers above Rodeo Beach that you simply don't get in August's persistent overcast. The Headlands Visitor Center at Fort Barry has water and restrooms; Rodeo Beach itself is a reasonable turnaround point if you want to cut the climb short.

Practical notes: the Caltrain-to-bike pipeline doesn't work here — you want to start from SF directly. The Presidio has free parking off Lincoln Boulevard if you're driving in, but BART to Embarcadero or Civic Center and riding through the city to the bridge adds maybe 30 minutes and is straightforward. Avoid the bridge sidewalk on weekend afternoons when tourist foot traffic peaks; the earlier you leave, the cleaner the crossing.

If you have two hours only: cross the bridge, climb to the first battery overlook on Conzelman, take the view, turn around. That's 10 miles and the best scenery on the route without committing to the full descent.