All the anti-wallers I have a question: If it isn't going to work then why oppose it? Just let is get built. Who cares?
My pro stance on a wall should not be confused with not supporting mine fields, MG emplacements and well placed claymores.
Mine fields and MG fortifications might be much, but actually patrols along the border by an armed military force would be sufficient.
Ideally, the border should consist of an 100-150ft zone that stretches the along the physical border. The area would consist of the wall, ~100 foot open, cleared space that contains a maintenance road, and at the end of the zone a chainlink fence.