The celebrated Ambassador Hotel, aging none too gracefully in its 66th year, has a new suitor--the Los Angeles Unified School District. The Los Angeles school board decided to explore the possibility of purchasing the Ambassador, razing most of the buildings and erecting a high school on the 23.5-acre grounds. Richard Volpert, attorney for the J. Myer Schine family, which owns the Ambassador, said he was unaware of the school district's interest. He said negotiations are under way with three potential buyers, with a price range of $65 million to $70 million. What the district proposes to do with the remainder of the property, including the fabled Coconut Grove nightclub, could certainly trigger controversy. Heritage-minded Angelenos have made preserving the landmark hotel a priority in their agenda. The Ambassador site is attractive to the school district because it needs to build a new high school in that area but has been unable so far to find a large enough site.