As cliche as it sounds, I found Tilley to have some great gear.
For a two month working-trip in Asia I brought one single pair of pants.
Something like this (although they have a few similar options):
http://www.tilley.com/canada_en/men/pants-shorts/pants/cotton-chino-pants-1.htmlYou can wash it in the sink and it's dry by the morning, and then you can re-pack it.
I know you'll be in bike-shorts while riding, but for meandering around towns and cities it's nice to look human
