Thanks to Bob M, checked it out today. Staying at Bally's and Google maps said the nearest BoA ATM was a mile away. Went to the M&M store! It is a very hidden dirty little secret. Love it!
Bob M hit the nail on the head -- the Bank of America "location" feature on their website mentions an "Ethel M's chocolate place" or something -- no clue that it's actually in M&Ms World!