Part of the problem with what they did in Yuma is that it was not done in Tuscon, so we don't know if the illegals who would have crossed over in the Yuma sector simply went further east.
Oh, and BTW, there also is a triple wall in the Yuma sector now. Thanks for making my point for me.
Fence in heavy traffic areas
Boot on the ground
Preditor drones
There is no point in only a fence and there is no point in attempting to put a fence in a river. There is also no way on earth you are going to get Texans to give over their water rights to Mexico by putting a fence on the Texas side of the river, and no way the Mexicans are going to let you put a fence on their side of the border.