Advice/Tips on running down walls
Your going to have to find a way to drill from the second to the first floor, unless you have a 9 foot drill bit:D . I usually try to go for a closet on the second floor, cut an access panel out of the back of the closet to drill on down. Then it's just a matter of fishing the wires from the attic into the closet and then from the closet down to the hole (or box or whatever)for the wire's final resting place. Insulation won't be a problem if you can stay on an interior wall, but keep in mind some bathrooms are insulated all around, so try to steer clear of that also.
Side note: There's no chance of coming up from the basement 'eh??