The idea of a wall is appealing in concept for those who haven't really studied the southern border, or visited the communities that straddle the boarder, most in complete peace and harmony and without criminals. Big Bend National park is just one area that helps explain why it is not so simple, and is likely a huge waste of money.
Border security could be improved greatly in many other ways, for a whole lot less. Cut the spending on nuclear weapons upgrades and you could fund it easily and a whole lot more.
The military secures area 51 and many other large secure facilities extremely well without building massive walls.
I don't want my tax money (and the future debt put on niece's and nephew's children) squandered on ill considered fantasies. We are running a HUGE deficit, value of my fixed income and savings keeps falling, and my food bill keeps rising.
There are many bigger threats.