Ir a un Equipo Deportivo, Apoyar un Equipo Deportivo (informal)

To be for a team, to root for a team.

In Venezuela most people are for Magallanes and Caracas baseball teams.
In Venezuela most people root for Magallanes and Caracas baseball teams.

In Modern Literature.

Mitch chuckled to himself. They rode silently on the interstate loop. "So who's gonna win the Super Bowl?" he asked.
"Oilers."
"Think so, huh? I'm for the Redskins. That's all they talked about in Washington."
The Firm by John Grisham.

In Dictionaries:

We're rooting for the college baseball team.
Oxford Advanced Learner's Dictionary.