What it SHOULD look like is this ...
Dear Mr Sanchez,
You are in the US illegally. We are coming to arrest and deport you at which point you will never be allowed to enter the US again.
However, if you take it upon yourself to return to Mexico in the next seven days, you will be allowed to apply for re-entry from outside the US under normal rules of immigration.
Your choice,
Homeland Security.
Winner winner chicken dinner!