This is a tricky one.
I know of one or two spawn points which are good for meeting NPC - (Carpark behind Concord, and the road down behind Cambridge police station near the fallen billboard, as you approach the corner of the building passing the billboard on your left.)
The tricky thing is this - sometimes, on certain characters, they work every time. And sometimes, on a different character, different playthrough, they don't work at all.
I guess it is a script fail that occurs early in the game, preventing NPC from randomly spawning ever.
I know one of my early playthroughs I never saw ANYONE at the carpark behind Concord, and then my last two characters I have met someone there (including mobs), each time I passed the location.
Like I said, it is tricky.