It will be Arena's chance to win a fourth MLS Cup.
"Two good attacking teams," Galaxy coach Arena said. "I expect to see some goals.
"I have no idea [what to expect].
"We'll see when we kick off on Saturday."
He added: "Last year's final, I think the weather conditions were a little bit of a factor.
"I think although there's a possibility of rain, it will probably be no worse than this, and it will make for a little bit more of an attractive game, perhaps a little bit more wide open. But who knows?"