Southwest has round-trip flights from Ontario, California (ONT) to San Francisco (SFO) for $59, NONSTOP. $29 each-way. Flights between February to May. No Holidays. Mostly on Tuesdays and Wednesdays. Origin/Destination reversible.
Note: You may find additional savings by booking your Flight+Hotel together as a package on Southwest Vacations. Before you commit, always compare the prices of the individual Flights and Hotel with other hotel booking sites like Expedia or Tripadvisor.