I have a quirky relationship with the Astros because I lived in Texas for so long and was an original season ticket holder for their AA team outside of Austin. Most of my friends were Astros fans (which made it fun for me to bring up '80), I preferred NL baseball, and Houston was a shorter drive/more interesting place to visit than Arlington. So they became my number 2 team. I didn't like the moving to the AL but with everything that has happened since then (increased interleague play, DH in NL) it doesn't seem like a big deal anymore. And it really has made the Rangers-Astros rivalry far more intense (though that is certainly no reason to start moving the NY or Chicago teams into the same league).
As a kid, the Brewers were my Strat-o-Matic team, and the Orioles, as with a lot of people in our region, were sort of my AL team until '83 got in the way.