You will get this achievement on day 18
First you must go to the Hi-Fi Store on the Eastside of the street and collect the tape from day 17. When you leave the store, a agent will take the tape and he wants to see you at 4.00pm right in front of Krank's drug store. Directly after the agent leaves you must go to the Moonwalker and tell Norma the truth. At 4.00pm talk with the agent again and you will see that Norma and Krank get away.
You will get a call over the radio that you have to talk to the press. Go to the Moonwalker and wait there for the news reporter. You talk with them and get the achievement Adiós Muchachos