Magid was in the right place at the right time to draw GB level towards the end of the first half.
The half finished with Gideon Barnett shown a yellow card following an altercation with a Mexican who was also cautioned.
Level at the break, Magid scored the winner with a brilliantly taken goal after dispossessing the last Mexican defender. He raced clear before slipping the ball under the keeper.
Caplin ensured the points with a smart tip over as Mexico finished strongly, hitting the post in the closing seconds.
Delighted GB boss Dan Collins said: "Mexico were a lot better than I'd expected. They made it hard for us but our fitness came through in the end.
"Credit to Marc Magid who did it when it counted."
Matchwinner Marc Magid commented: "For the oldest man in the team, I'm not too bad."
