Here's what I always recommend to our Warmshowers guests for getting out of SF:
Baytrail to Redwood City; Middlefield Road to just over the Palo Alto town line; Palo Alto Ave, which turns into Sand Hill Road, to Old La Honda; Old La Honda to 84, to Pescadero Creek Road, and out to highway 1 on Pescadero Creek Road.

It's much less nerve racking than Highway 1 south from San Francisco (which doesn't have enough shoulder on the uphill stretches for me to be comfortable riding in traffic with tourists looking everywhere but at the road). Most is on very quiet roads or MUPs, next to the Bay, or through redwoods.

Old La Honda is 1300 feet of climbing, but it doesn't get steeper than about 7% except in a couple of places. (I think 1 out of SF is steeper.) I'm fat and slow, and I've done it loaded.

One caveat: I would avoid Old La Honda at lunch on weekdays, as it is a favorite training ride for the lunchtime racer crowd. (Every cyclist who lives on the SF Peninsula knows their time up Old La Honda.)