Background:
I'm taking a 31 day trip through Peru from Lima up to machu pichu and around to colca canyon and Nazca and more then over to Bolivia to see the salt flats rugged landscapes and mining towns. Previously, I spent a month going around Thailand and had brought a few lenses but didn't use all them so they were dead weight.
Current:
Based on my current usage I've actually sold off the lens I didn't use (EF-S 17-85mm f/4-5.6 IS USM). I've upgraded my body from a 300D to a 40D and added the EF 24-70mm f/2.8 L USM to my line up.
I suspect the 24-70 will stay on the body for the most part I am wondering what other lenses people think I should take with me? To date the 70-200 has always got left behind due to weight.
Looks like a great setup for a trip to me. Obviously you are planning to stick to wide shots, and if that's your focus then you have it covered. The 50 1.8 is so small and light, I'd probably throw it in the kit just incase you need the speed, but otherwise it looks good.
I'm jealous of the holiday. Peru is on my list of places to go soon.