Best Canon lens for travel? I'm looking for a walkaround "all-in-one" lens with a good zoom? - good all in one lens

I have a Canon EOS 5D Mark II and I need a good goal for the trip. I can not have four or five glasses everywhere I go, especially during the holidays, I would like to purchase a lens with good zoom, auto focus and USM. I'm getting to 2.8, but f / 4 is also acceptable.

Oh ... and I would therefore not too expensive. In probably less than $ 1000 (hopefully under $ 1,000, but I know it is not likely)