I put off attending UCLA for financial reasons since my stipend was tuition and books only, so I wanted to work a year or 2, save up, and then go. Never got around to it.
I have been a fan of all 3, but BYU has always been first and foremost. I have started rooting against anything PAC 12 most of the time recently, but since I have always rooted against anything east of the Rockies, we'll that gets conflicted at times.
I grew up in Utah and generally supported all teams in the state.
I have lived in Chicago twice and followed Northwestern a bit. Bosses and co-workers were often ND, OSU, or Michigan fans. I followed those a bit.
I have lived in Orange County, LA, or Ventura County in So. Cal most of my career. Used to like PAC. Not now. Still usually root for MWC teams.
I lived in Hawaii for 10 years. Love the Rainbow Warriors most of the time.
Lived in Las Vegas for 1 year - sympathetic to UNLV.
Bottom line, and I didn't even mention professional teams, BYU is my team and I have a little interest in pro teams with BYU grads.
That is it. BYU. Go Cougars!