100 ISO film is ideal for night photography. Use a tripod and a shutter release cable or remote as well as the self timer if you don't have mirror lockup.
50 ISO film is fine too, but I'd recommend you not try using it till you have some experience shooting at night.
Here you go, a few exposure times to work from.
Dimly lit streets.
8 seconds, f8, 100 ISO
Floodlit buildings, fountains, and monuments. Subjects under bright street lamps:
4 seconds, f8 - 100 ISO
Fairs and amusement parks: 1 second f8 - 100 ISO
Brightly lit streets: 1/2 second f8 - 100 ISO
Brightly lit city squares eg: Times square in NY, Piccadilly circus London etc.
1/4 second f8 - 100 ISO
City skyline 10 mins after sunset, Neon Signs.
1/8 second f8 - 100 ISO
Don't foreget that these are a rough guide only, fine tuning is required and I recommend you bracket the exposures at first with +1 stops and +2 stops till you get the feel for night photography. Try to keep your exposure times under 10 seconds for Kodak film (eg Gold 100) and 16 seconds for Fuji, otherwise you'll run in to reciprocity failure and the joys that brings with it.
I used to shoot 25 ISO at night for architectural work for clients and since the demise of KM25 I now use 50 and 64 ISO emulsions instead.