I would think the following catagories would automativcaly know how to drive a stick:
Gear heads and mechanics
People who are crazy about cars or a specific model. The Volkswagen bugs for example have a following as do VW vans and most are stick.
Guys who spent alot of time in auto shop in school
Rural people most know.
Motorcyclists, most you shift.
Speed freaks,
Folks who worked construction or on or around heavy vehicles and equipment like construction.
I would say that if your characters had those backgrounds then they would most than likely have the ability to drive a manual.
However, the familairity with that type of stick shift is another storey, even I ONCE only ONCE had problems with a manual I was unfamilair with, it was backwards, reverse was where 1st is normaly at.
I today have two stick sifts and the reverse is in yet another different place, it is where 5th is on my other truck, to the right more than normal and up, whereas it is oposite on my other truck, the thing is both are dodges, although one is japanese made. And then the FIAT is normal lol well when it runs that is
