I'm one who thinks the 'no cotton' rule can be overdone. Sure I want wool or synthetic/wool mix when things get exceedingly cold and wet but other than that I am not going to junk cotton for synthetic in warmer climes. Some things are simply not negotiable and wearing plastic clothing is one of them.
That said, it was with some sadness that I have had to admit that 501s and snake skin boots are not terribly practical on board.
Eryka is right....chino type pants are the go even in my opinion if cotton. Reality is that in moderate weather light weight cotton pants are not a serious problem if only because today's boats are not as damp collecting as they once were.
On my first (timber) keelboat I could not leave clothes on board for any lenght of time without mould developing or at least a nasty musty smell. On Raven in 2010 I leave some clothing on board at all times and mould and damp is simply not a major problem. Yes is can be a problem after say a rough passage combined with wet weather after but a bit of wool covers that eventuality.
Oh yes....wool or even better possum socks.