When I go city-scape shooting, most often in Chicago, I like to take my 24-105 and one other lens, usually the 16-35 as I now have a 5D iii. But last time I went to Chicago, I took the 135 instead of wide angle. I got some stunning shots with it and realized after getting home I should have kept it mounted longer.
What I do is use a Lowepro lens case attached to my belt big enough for the larger of the 2 lenses I take. That way I'm free to walk wherever I want without dragging a 'ton' of gear...bags, etc.
So I have to ask, what are your 'limitations' for the trip?
Are you flying there? - carry-on size issues need to be considered.
Are you renting a car? - if not, then what's comfortable while walking is a limiting factor.
Are you staying in the downtown only?
Are you alone or with someone? - If you're on foot, having an extra 'mule' doesn't hurt (she may start talking 'divorce' though...)
Are you at or near retirement age? - I am, and my time walking around gets less every time!
One other consideration...who will be viewing your pictures? My cityscape shooting is largely for myself, so getting hi-res, perfectly exposed/post processed pictures is becoming less important. I'm primarily after the memories, old ones renewed and new ones. I recently picked up a G15 point and shoot for 'banging around' (eg, personal use) and am considering using just that on my next trip to Chicago, and LA, on my vacation 3 weeks from now. On the other side of the coin, however, a couple of downtown Chicago shots with the 135 f2L are some of my best shots in 50+ years behind a camera!
Consider your goals/desires, and limitations or restrictions, if any, and come to an appropriate decision. I'd probably go with all 3, carrying 2 in Lowepro cases, as they are all reasonably small.
Edit: 2 more questions..considering the value of your equipment, is it all insured? Is physical security OK?