This domino game is said to be played in San Lorenzo, Puerto Rico and Guadalajara, Mexico. It is for four players, each playing for themselves.
A double six set of 28 tiles is used, and each player takes seven. The holder of the [6-6] begins by playing this tiule, and play continues counterclockwise.
When a player goes out, each of the other players scores the pips on the tiles that they are holding.
If the game is blocked, then provided the player of the last tile has the lowest score, everyone scores the pips on their remaining tiles. But if some other player has a score less then or equal to that of the player of the last tile, then the player of the last tile scores four times the number of pips in his remaining tiles, while the others score just the number of pips they hold.
Seven deals are played, after which the player with most points is the loser and must buy beer for the other players. The scorer normally keeps the cumulative scores secret (though players with good memories and arithmetical skills may know them anyway) until just before the seventh deal, when they are announced to all players, so that players know what they need to achieve in the final round.
There is a decription of Gallinazo on Jose Carrillo's page, and this in turn was based on Alfonso Garcia's web site.