I am a practitioner of the leisure arts and an unapologetic optimist. I live a gluten free life, happily. I like to cook and challenge myself with recipes and techniques. If you had fun, you won!
It would be a real shame to starve in San Francisco with all the great food! You could always stop by a market or the Ferry Building on the first evening and stock up on snacks. Also I agree that there is likely a gluten-free restaurant that would deliver for you. I do hope you get what you need!
I have a cafeteria at my workplace and I cannot seem to communicate my needs no matter who I talk to or what I say. Now I skip lunch or go home. It is annoying though, especially because egg and nut allergies are taken so seriously, as are veg and vegan diets.