Avis is involved in talks on the possible sale of the company, an official of the nation's second-largest car rental company said. The options under discussion include the sale of Avis to its employees through an employee stock ownership or a sale to the public through a stock offering. The official said no timetable has been set for making a decision. Avis, based in Garden City, N.Y., could fetch around $1.75 billion for its owner, Wesray Capital Corp., a privately held company specializing in leveraged buyouts. Wesray investors, including Avis management, acquired Avis in July, 1986, from Beatrice Cos. for $265 million in cash. Wesray also assumed $1.34 billion in Avis debt.