Need suggestions for walk around lens that is good for street / low light shots

[aakash_vakil]

Hello -

I use Canon Rebel XT and team it up with a Canon 50mm 1.8 for my street shots. I have a 18-55 kit lens but i rarely use it these days after getting adicted to 50mm !!

I am going out on a weekend vacation and will be doing a lot of walking so looking to reduce my gear weight.....and a lot of steet pictures at night time / lit up buildings after sunset so looking for a fast lens.

Prefer a high quality zoom in 18-85 range but if that means compromising image quality then i dont mind going for a prime as well......

Any suggestings on the lenses as well as lens rental shops in US.

Thanks!
Aakash