Hi @mouse. I'm a Brit living here and happy to give you a European perspective on food. I have to tell you that the food here in Northern California is some of the best I have eaten anywhere in the world. However there is a BUT.
I love the Farmers Markets and as you say the Ferry Building is great. The problem is that it is very expensive to source great ingredients and it is easy to get overwhelmed by the not so great stuff here. I just buy for one and I spend as much here for me in one week as I do in the UK to feed two.
I shop mostly at Whole Pay Check and even there, the first thing you see is racks and racks of tortilla chips and the most mind boggling array of dressings I have ever seen. Now that might be better than in the UK where you are confronted with racks and racks of wine when you go into a supermarket, but to a European eye its odd. Because you are catering for more people here, the veggies often don't have much taste and so I always buy organic (but often they are not really organic).
You have to read labels really carefully here. I notice many more additives than in Europe in the foods. On the other hand, if you have allergies, there is nothing you can't get and there is no excuse as things that are hard to get in Europe are freely available here. I have however had allergic reactions to fairly innocent items such as fresh raspberries.
Eating out is challenging because it took me six months to learn the system - as you say - share an entree. San Francisco has some of the best restaurants in the world, but in many average restaurants somehow there is always one ingredient too many piled on top. This is often a US thing I find, but finding a restaurant that will do fish, simply broiled, no sauces, not farmed can be challenging. I get weird looks every time. Shrimps often have a strange aftertaste to a European palate, like they have been somehow pasturised.
It's not all bad. I LOVE the sweetness of the fruits here and the range and availability. Young coconuts you just can't get in the UK very easily at all. Same with veg, eg the range of beets, daikon, types of kales etc. I also like the fact that grass fed beef is easy to obtain. Ahi tuna - never see it in the UK but I would eat it every day if I could afford it. Coffee - yay! well, its San Francisco and I'm glad you guys are lunatics about coffee quality.
I am a fan of Grain Brain and when I'm good I eat no sugar and no grains, but I do eat brown rice

. The absolute worse thing about living in America? Sugar or corn syrup in everything. WTF??