It's to the left of the centerfield gate, back towards where the stairs to the parking garage exit. Go to the gate, turn left and go until you almost hit the wall, turn right, and it will be on the left. It's open game days too, but it's busier. There's also one inside the park that's open before games on the first base side on the 100 level by where the ramps to the upper levels enter, but it's always looked packed.