The problem, I think, with holing up in rural areas is that everyone
will try to do it. And the people there already will defend it to the death - because the alternative is to die anyway. The only way you'll get onto a farm is if:
A.) You're already on one.
B.) The person who owns the farm is a close friend or relative.
C.) You're prepared to kill the people already there.
D.) Someone in the farmer's group shoots your son in a hunting accident.
Everyone is going to flock to the countryside and it'll likely be more violent out there than in city areas. I wouldn't go near a skyscraper as it would end up being a very tall tomb. I do, however, think I would prefer to take my chances in a more urban environment. Maybe not a full blown city but certainly a medium or large town.
A boat could work if it was near enough the shore for you to go gather supplies when needed, weren't worried about the possibility of pirates and you didn't mind living off fish. A rural area or skyscraper, to be blunt, will not work.