I took my 40D last August to Chicago. I also brought a 17-85mm and a 70-200L IS. The first day I quickly realized that there is no way I'd be carrying the 70-200mm beast with me. It definitely stands out, and is just too heavy to carry around. I was also worried that I'd be standing out with my camera - period, but soon realized that everywhere I went, there would be about 5-10 other tourists with their cameras around me so I "blended in" without any problems. I definitely advise you to take the widest angle lens (for architecture shots), and extra memory cards with you. Pack lightly, and have fun.