For backpacking, I use convertibles. Then I have a pair of pans when I need them. I am quite fond of Eastern Mountain Sports attire. It's the right price for the quality (which is equivalent to it's competition i.e. Columbia, North Face etc)
Men's Shorts - Men's Pants & Shorts - Eastern Mountain Sports
Good advice I wear the same when backpacking. Many times it night to have the pant legs. Also for backpacking I recommend staying away from cotton. Nit everyone will agree with that but personally I will NOT wear any cotton when backpacking. I might for a day hike but thats it.