OK 1st of all I would like to know the best place to rent a lens from but this isnt the main thing
What lens to rent. I will be in the market soon for a new walk around lens. I am attending a photo walk on oct 5 and it will be in an urban environment. More than likely street photog. Anyway any suggestions on renting a lens
I would go for the 17-40 from LensRental. It is the classic pretty wide walk around for Canon. Or you could go for wider with the 10-22, or narrower with a variety of chioces, the Tamron SP AF 28-75mm f/2.8 XR Di (I used an older version for my walk around), or any number of good chioces which are debated well over here at DPReview
I would go with the 24-105 f4 L. I like my 28-135 as a walk around because of the range, the 24-105 would be the closest high quality lens near the same range.
If you're going to be in a city, there is likely a local place you can rent from that would save the trouble and cost of having to ship the lens back and forth.
a 24-105 is a bit on the big side if you're going be walking around for a long period of time, it does cover a good range, though.
i think the 15-85 is a good suggestion.
eta...
thinking about it more, the 15-85 extends so it would also end up being kind of big. for me i like a smaller, less conspicuous lens when shooting street.
If you're going to be in a city, there is likely a local place you can rent from that would save the trouble and cost of having to ship the lens back and forth.
unfortunately there are no rental places anywhere around