That is a fine looking wheel set you've got there
Not sure what the trailheads look like in your area, but I probably wouldn't think twice about leaving my jacket and pants and boots slung over the seat in plain view when the bike is parked in the woods amongst other outdoorsy types, especially with that bike rack hanging off the back. However, a PacSafe locking bag is still cheaper than new gear.
Edit: Just saw who the OP was. I've read the IBA posts on your blog, great stuff. In that case, I'd buy as many locks as you can; those New Yorkers are animals.