I'm with Meysha on this one - a slower ISO film (say 100, or even 50) with a sturdy tripod and a longer exposure will give you a less 'grainy' image, and generally better colour saturation.
If you're planning to shoot under street lights (the orange sort), you could try using Tungsten-balanced film (Fuji RTP II for example, ISO 64) to give more natural looking colours. If you can't get hold of any of this, a blue filter (80A or 80B for example) with regular 'daylight' film will have a similar effect.