Tons of close hotels, but they're expensive. You're better off in Mission Valley for your money. From there, the trolley will take you downtown.
Go with the Mission Valley + Trolley route, NOT National City! Mission Valley is full of eateries, shopping, other conveniences for the day before or after the game, not so with scary National City.
You can find cheaper hotels in Natiional City or Chula Vista which are 8-12 minutes away.
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