To the poster that said the first half was more efficient..uhhh... no, it isn't. It is infact the reverse as you have to tote around that extra gas.
What you are experience is the fact that most fuel gauges are ridiculously inaccurate. As a general rule, they stay pinned at full for 100 miles or so, then drop like a rock.
To the OP, I have a '97 Saturn 5 speed also. It is a SW2 (DOHC). My daughter drives it most of the time. the DOHCs are shorter geared than the SOHC. If you are not sure which you have, XX1 means single overhead cam, XX2 means double overhead cam. The nice thing about the short gears is that on level ground, you can short shift very easily. I find this thing will idle along in 5th rather happily at 25 mph, maybe even a little lower. I usually skip shift from 1 to 3 to 5 unless going up a fairly decent hill.
Something I don't like about the saturn is that it does not seem to have DFCO, so an ignition kill switch would be a good investment.
As for the fuel gauge, as I said, I don't drive it that much, but, I have noticed that unlike most cars, it drops quickly during the first half tank to the point where it is sitting near E and it still has nearly a half tank left. I drove it last week to Mass (about 20 miles). When I left the house the gauge was almost on E, close enough that I stopped near my home, to get gas rather than risk the drive to mass where gas is 20 cents cheaper. I just put in two gallons and the needle shot up to about 1/2. Later in the day, in mass, I filled up and it took just 6-7 gallons.
As for driving in Manhattan, why do you?
I ride my bicycle to work, about 12 miles. Well, I do when I'm not being lazy.
I highly recommend it to anyone that can do it. Street riding is a little adventurous in the city, but, many do it. Also, I do believe there is a pretty good network of bike paths. And if you can't ride, how about the train/bus? Mass transit isn't practical for most people in the US, but, it is very practical for you.