Central Park, on a summer evening in 1981. A not-yet-famous John Goodman and Mandy Patinkin were dueling during a dress rehearsal for the New York Shakespeare Festival's "Henry IV, Part One," directed by the not-yet-famous Des McAnuff. Suddenly the sword flew out of Goodman's hand and appeared to land on the noggin of an even more obscure young actor named Benjamin Donenberg.

The festival's legendary producer, Joseph Papp, dashed onstage and asked Donenberg if he was OK. The unhurt greenhorn replied with one sentence only: "Now Joe Papp knows who I am."

Los Angeles, too, is beginning to know who Donenberg is.

Having consciously modeled his Shakespeare Festival/LA on Papp's--indeed, using budget formats that Papp loaned him--since 1986, Donenberg (now known as Ben instead of Benjamin) has created alfresco productions for audiences that have grown from 800 in the first year to 22,207 last year. This summer, for the first time, the 36-year-old producer will do two plays instead of his customary one.

The festival's first tragedy ever, "Romeo and Juliet," opens on Saturday. Previews began at the John Anson Ford Amphitheatre Wednesday. As usual for the festival's Los Angeles productions, admission is free, but playgoers are asked to bring cans of non-perishable food that will be donated to the Salvation Army and AIDS Project Los Angeles. (Last year's show netted food valued at $100,000--a sum tripled by Vons.)

Next, "The Two Gentlemen of Verona" is slated for a July 29-Aug. 8 paid-admission engagement at South Coast Botanic Garden near Rolling Hills Estates. Depending on how much money is raised between now and then, "Verona" may move to the festival's traditional downtown L.A. home, Citicorp Plaza, for an Aug. 12-22 run with no admission charge. But even if "Verona" doesn't make the move, the festival will stage a one-hour version of "Romeo and Juliet," using youth from Nickerson Gardens, at Citicorp Plaza in an early evening slot, Aug. 13-15.

Shakespeare Festival/LA is tentatively expanding in an era when many companies are contracting or dying. The most obvious comparison is the recent collapse of GroveShakespeare in Garden Grove. In an interview, Donenberg--who has never been to any GroveShakespeare productions--expressed regret at the moribund company's plight. But Los Angeles is more willing and able to support a summer Shakespeare festival than was Garden Grove, he claimed.