Vacation to Greece (Lens Suggestions/Advice Needed!)

I'll be taking a 10 day trip to greece coming up and am looking to add another lens that will make the trip easier to shoot.

As of now I have a Rebel XS (happy with this, still takes great pictures for how outdated it may be ). I have the stock 18-55 IS, and a 50mm 1.8 as of now.

I've been looking into the Sigma 18-200 or the Canon 28-135 as a good walk around lens.

Do you have any suggestions? I'd like to take alot of street photography at the markets early in the mornings as well as some architecture and landscape photography.

We'll be in Athens for 2 nights, and a mixture of Mikonos and Santorini for the remainder.

Any suggestions/tips would be greatly appreciated!

I used my 28-135 on my Rebel XT. Worked great for most situations.

These gallerys were all taken with the XT/28-135 combo.

Nafplion:
http://vang.smugmug.co​m …70_dRrPhh#69024​6955_hYd7Z

Katakolon/Olympia:
http://vang.smugmug.co​m …48_SQLtq6#69025​9239_jRT8y

Corfu:
http://vang.smugmug.co​m …40_G9d5bW#69027​4510_VQc2f

Mykonos:
http://vang.smugmug.co​m …44Sq7z#14282093​66_Nm537rS

Santornini:
http://vang.smugmug.co​m …3h2nBk#14283432​92_n3nFWDx

pitrow wrote in post #13176691
I used my 28-135 on my Rebel XT. Worked great for most situations.

These gallerys were all taken with the XT/28-135 combo.

Nafplion:
http://vang.smugmug.co​m …70_dRrPhh#69024​6955_hYd7Z

Katakolon/Olympia:
http://vang.smugmug.co​m …48_SQLtq6#69025​9239_jRT8y

Corfu:
http://vang.smugmug.co​m …40_G9d5bW#69027​4510_VQc2f

Mykonos:
http://vang.smugmug.co​m …44Sq7z#14282093​66_Nm537rS

Santornini:
http://vang.smugmug.co​m …3h2nBk#14283432​92_n3nFWDx

perfect, i literally just sold my kit lens and picked up an 28-135 yesterday. i'll be taking that along with a 50mm 1.8 shot for early morning market/vendor photos.