Walk around lens

Completely agree that the 18-55 would be my first option, plus the rectilinear Sigma 10-18, unless he wants to try also fish eye, who is very interesting but not suitable -IMHO- for all situations.

From my last trips I checked the ExiF data for a sample of my city landscapes and found that about 90% were shot below 30mm, most of them at 18mm. I could have used a lot of the times something below18mm, which is why I may recommend the rectilinear Sigma 10-20mm (non fish eye lens).

If the OP has access to the WR 18-135mm that's a very versatile lens for vacation/walk around, but something wider than 18mm always is desirable for city landscaping. I wouldn't take a long tele/zoom to NYC, but that would be me.

Actually the person I bought the kit lenses for my K-5 went to NY (also to San Francisco), he got excellent pictures and he took the 18-55mm and 55-300 as his only lenses. He has excellent pictures posted in Flickr and most of them are taken at 18mm.

What you can do is check Flickr for pictures of NY, download them temporarily in order to examine the EXIF data and you can see all the characteristics of the pictures. You also will get an idea of the time of the day and day of the year when the shot was taken. It's a good way to understand also what settings were used (ISO, f/shutter speed, program mode, ev compensation, so on).

These are some samples using the 'maligned' 18-55mm kit lens:

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