Aside from when you're riding for exercise or competition (when lycra is proper), why not just wear what cycle-commuters have been wearing over a hundred years: pant-leg straps. (They don't have to be the dorky reflective ones. They cost nothing and they readily fit in your pocket or can be wrapped around your seatpost when you don't need them. )

You can wear whatever pants you want, and you virtually eliminate the risk of getting your pants ripped up in the chain.