When early summer's fog and wind get you down -- or even when they don't -- step into the tacky tropical Tonga Room for an instant dose of vacation spirit. It's plastic Polynesia for sure, but surrounded by tikis, tourists, and $6 all-you-can-eat plates of greasy grub (weekdays from 5 to 7 p.m.), you can't help but get into the umbrella-drink groove. Linger long enough for the thundering rain shower, or seriously go the distance and hang until 8 p.m. for live entertainment (except Monday and Tuesday) by the Mirage, which sticks to the kitsch theme with pop hits performed from the dining room river's centerpiece barge.