Plumlee (17) flies to Los Angeles on Saturday to spend time with his Californian-based family, before heading to Argentina on July 17 for the month-long trial.
He played his last games for the Waitaki First XI, which he captains, and Meadowbank United on Saturday.
He plays for the school on Saturday mornings and for Meadowbank United, in the South Canterbury first division, in the afternoons.
Plumlee has played in the First XI since he was in year 9.
In 2008, he was a key member of the team which won the Otago competition, and also played in the Otago Under-16 team.
Last year, he was a member of the Otago United Youth team which travelled to Northern Ireland for the Milk Cup, which he described an "amazing" experience.
"Knowing you're playing against the top youth professionals at the time is just crazy," he said.
Plumlee admitted being nervous about the trip but said he planned to see how far football could take him.
Waitaki Boys' football coach Andy Lane said it would be an intensive trial and Plumlee would be watched constantly throughout training and games.
Regardless of whether he managed to secure a contract, it was going to be a "fantastic" opportunity.
Plumlee had made "tremendous steps" with his tactical understanding of the game.
A midfield playmaker, he created a lot of goals, and he would be a big loss for the school team, Lane said.
Plumlee has also gained coaching qualifications and helped with junior football at the school.
