They were cheering Jason Castro and likely heckling Ozzie at the same time. Jason doesn’t have a beard so why wear a fake beard to promote the Houston catcher? They could have just as easily claimed they were Brian Wilson fans.
I don’t know if you are from the Houston area, but in the last few years a small group of fans have been dressing up for games as:
1.) Vaqueros, complete with little toy horsies and big hats to cheer on Carlos Lee (El Caballo),
2.) Pumas (large felines), complete with head-to-toe furry costumes resembling cougars, to cheer on Lance Berkman (The Big Puma),
3.) Bees, complete with striped backsides and silly antennae, to cheer on Bagewll, Biggio, etc. (The Killer Bees).
The Castro thing seems a natural, although perhaps a little silly given that Jason is fairly unremarkable so far, and fidel is such a monster that it seems in bad taste regardless.
Oh, and the folks were not only wearing obvious, comically fake beards, they had on silly cheap sunglasses, jaunty berets and had big cigars and little Cuban flags in their hands.