Myself, due to my more usual subjects and my own habits at the street, usualy have my camera setted at the 3m mark and from this starting point I easily fine focus any subject in the range of 1,5m and infinity.
If I am within a bus, for example, and my subjet is sitting at an unknown distance close to me, I preset my camera to 1,5m and I know I will have a nice juxtaposition to start focusing my subject, provided she/he is sitting between 3m and 0,9m. I will raise my camera, fine tune my focusing in a fraction of second, and be able to fire at will.
This is my solution, but by no means the only one. RFF member VinceC, uses a much more refined way. Before raising his camera to his eye, he guesses the distance, set the lens accordingly and then fine focuses the necessary bit.
Cheers,
Ruben