Get Tons of Points
Start a two-player game and proceed to strike out every batter on each side until the bottom of the ninth inning.
When you've got two outs at the bottom of the ninth, walk the next four hitters to earn enough points to buy 100 card packs, which should get you almost every card. If not, repeat and get yourself more card packs.

PS2 Cheats for All-Star Baseball 2004

All-Star Baseball 2004 cheat codes

All-Star Baseball 2004 cheats