Remember that more gears doesn't necessarily mean lower gears!

You can get 6 speed megarange freewheels just as easily as 7 speed megarange freewheels.

There would be a slightly bigger gap or two in a 6 speed, but the range from low to high would be exactly the same. In fact, I don't know of any cluster that offers a larger cog than 34... The jumps are smaller, and with some, the high gear is higher (11 tooth on a cassette versus 14 tooth on a freewhweel), but the lows are no lower than they have been since the first meagarange.

If I were riding in SF, I would need a triple, or a compact double, either one with a megarange cluster... Then I would probably walk up many of the hills anyway.