FWIW, Dave, I think you made the right choice. The 17-55mm is not weather-sealed, so do try to stay out of the rain...a little bit of drizzle for a brief period won't hurt (it hasn't hurt mine, at any rate). I have both the 17-55mm and the 24-105mm - I got the latter specifically to shoot with the 7D in the rain, but the 17-55mm saw a lot more use than the 24-105mm (saw, because I use the 24-105mm a lot now, but that's on the 5DII).


The UV filter is great for protection and easier cleaning - be sure to use a good quality one (I use B+W MRC UV filters on all my lenses). It won't help with the water - the main entry points would be the switches and zoom extension, as well as at the lens mount.


Again, have a great trip!


--John