Originally Posted by rowan

Just remember that on your 20D a 24mm focal length will be the same as a 38.4mm lens on a full frame/film camera, due to the smaller sensor.

Are you ordering by mail or can you go in and see it?

You could probably even get away with the 18-55mm EF-S kit lens for starters, and figure out where you need to go from there. Better to spend +$150 on the kit lens than $1600 on your L glass and realise the zoom range isn't sufficient...?