The largest amount of cash I have ever carried with me was 650$, which I carried about a mile and a half from the bank to my landlord's place to pay the rent, in broad daylight.
As to how much I WOULD carry with me, it depends. If I'm planning on walking somewhere (more than a block or so in a residential neighboorhood), probably not much more than that. If I'm just going to hop in a car, go the the atm, hop back in the car, go somewhere, walk from a parking spot right outside into a building, and give it to someone (say a car payment), I'd be comfortable carrying a lot more, maybe a few thousand (assuming I had that much). OTOH, walking alone down an ill traveled road, or at night, I would carry as little as possible.
Metherion