The AF / KLM lounge at SFO is a bit of a sad affair, not usually any particularly good food or drink. The best food / drink in the concourse is at the end of the Terminal at Valencia Station, but it's not great.
Best to get a great meal in in SF (or go to In N Out near the airport!) then just hop on your flight - or of course, eat on board!
Enjoy your La Premiére experience!