I was doing some research on her father Gottlob Gall and found him listed in the Langley's San Francisco Directory each year for over 20 years (from 1884-1905). By the way those directories are available on sfgenealogy.com. He was a baker, and during his time in San Francisco he worked at and eventually became the proprietor of the "Volz & Gall bakery & coffee saloon" which was located on 28 4th St., just off of Market St. Here is a listing from 1895.
In the same directory I also found an entry for Benjamin's mother Julia. She worked at a cigar and tobacco shop, that just happened to be across the street at 41 4th St!
Assuming that this is indeed Benjamin's mother, I don't think that I could get any closer to finding documentation that proves this story, short of having the love story printed in the San Francisco Call itself. The fact that their parents both worked across from the street from each other would definitely put them in close enough proximity to bump into each other and fall in love.
The address of the bakery (28 4th St.) was in the Pioneer Building. So it would have been one of those little shops that was at the bottom. Today that building is an Old Navy, but back then the building was different. Across the street is a modern day Marriot where the cigar shop would have been. Here is a picture of the Pioneer building from 1888.
Then in 1906 San Francisco had it's famous earthquake and most everything was damaged, either in the earthquake or in the fires. Here is the same Pioneer building in 1906. You can see that the shape of the windows are the same.