Yes we should build a wall, and many other things to make it as difficult as possible to keep people who want to break our laws out.
Right now we have about 11 million illegal aliens in the US, we have no clue on who they are, why they are here, we do know they don't respect US law. So basically we have 11 criminals in the US and they should be deport upon their arrest, and business should be fined at least $10,000 per man hour worked with an assumption they worked 2040 hours unless said business can prove they didn't work that many hours.