No. They won’t. At all. Any nitwit can walk. Very few people in the world have the resources to “tunnel” under the wall. Very few people have the resources to fly in on illegal flights successfully. Very few people have the boats to come in through the costs (which is heavily guarded by the Coast Guard anyway).
People do what is necessary and they usually do it in the easiest way possible. Like if you lost your job delivering Pepsi, you’d still need to eat your usual dinner of cheetos and bean dip. So you will find another job delivering Papa John’s pizza or something that is probably not as challenging as that would be for you to get your cheetos and bean dip.
The people crossing the border, if they think its necessary to come across will simply find another way; paying smugglers to ferry them across by truck or boat.
As for the Coast Guard…how successful have they been in interdicting the cocaine from Colombia? I’m sure there is no coke on the streets…right?