The SeaBees could do it in a week. All it would take is to promise them a steak dinner and free some beer.
Duncan Hunter talks about 6 months for the 854 miles of fence that was already approved. That is less than half the total needed (IMO), so I’d go with the razor wire in the meantime.
I just looked and found a company called Cochrane that makes machines that can string a pyramid of 6 coils of razor wire at a rate of 25 miles per hour !