California fare sales to Portugal are uncommon. Delta, KLM and Air France have San Francisco SFO to Lisbon and San Jose SJC to Porto, Portugal on sale for $483 to $518 round trip.
Travel departure dates: late October 2017 – mid-March 2018.
Delta Airlines SFO – Lisbon, Portugal
$507.76 round trip
Delta Airlines San Jose SJC – Porto, Portugal
$518.66 round trip (19 hr overnight in Amsterdam on return).
Lower airfares can be found on Momondo.com.