While your friend's out there taking care of the pig problem, have him inquire about damage to the irrigation lines. If there is any, let them know they probably have a coyote problem - coyotes will chew them to get water - and offer to "help" out, for free of course.
Vineyard hunting is like orchard hunting - your field of fire is extremely limited, mostly shotgun work for sure. For something like that, do some preliminary scouting using Google Earth and find the access and maintenance roads, pump stations, shit like that, then maybe plan your shoot on those instead of actually inside the vineyard. Google Earth will also help you locate any outbuildings so you don't pepper them by mistake.