There's a slight air of San Francisco, both its fine air and its funky, this week in Mount Vernon Place, site of Baltimore's Washington Monument.

Informality and the under-30s dominate the stately space. Within walking distance are 15 spots playing host to TNT, The New Theater Festival, which began five years ago at Ann Arbor's University of Michigan and moved, for the last two Junes, to the University of Baltimore's Catonsville campus.

Under Mayor William Donald Schaefer's agressive campaign to vivify rebuilt downtown. This year's TNT contributes some of that casual color which so often brightens San Francisco. There are street entertainers - jugglers, mimes, singers, dancers - putting on planned or even impromptu shows. There are food vendors for crabcakes, tacos, hot dogs, hamburgers and crepes and stands where you can cool the innards with beer, lemonade and herbal tea.

During the week there will be 150 events, including performing groups from this country, Japan, France, Canada, Poland and Belgium as well as Washington's The Marianne Marcellin Attic Theater and the Cro-Magnon Funk and Arlington's Seventh Dawn.

In eight hours, I saw a half-dozen attractions in such cooperating spots as the Peabody Conservatory, the "Ys" - both "M" and "W" - and the Cultural Arts Project and observed workshops and groups in several area parks and churches.

"The New Theater" is another term for avant-garde, each generation's effort to expand previous boundaries. Inevitably, this leads to probings that can be absurd, painful, repetitive, pretentious, asinine, irritating, exhausting and marvellous.

Since in eight hours of wandering, I did find one group that was marvellous, the trip was worthwhile.

That is no mean matter, for with their necessary adaptations of makedo spaces, festivals have their physical challenges. To watch a boring show in the most comfortable circumstances is torture enough, but in conditions made fashionable by Poland's Jerzy Grotowski and his "Poor Theater," the boredom can be excruciating physically.

However, I was physically comfortable for "Le Plan K," founded five years ago in Brussels by actor-director Frederic Flamand, aiming "to explore new relationships between the text and theater and between voice, props and musical instruments," common credos for the avant-garde.

Two male performers appear in Flamand's "Le Nu Traverse," which further involves a wooden-metal mannequin, a helmet which becomes a musical instrument and a long metal pole that initially appears to go through the heads of a performer and the mannequin.

Their performance begins around what might be a white, round scatter rug but which turns out to be small chipped stones that eventually will be splattered over the entire playing area, around four sides of which the audience is seated. One of the men takes to winding up, then carrying around, an ancient portable record player, sending out schmaltz and pure Bach, which, if you've ever considered such, is an impressive balancing fear. At the same time he manages to slip off the jockey shorts of his partner, who then rolls around with the mannequin on the stone chips and pieces of broken, 78 rpm discs. They gradually disappear behind a black curtain.

This sort of assured, physical endurance, accompanied by reiterated grunts and shouts in French and English, is what gives avant-garde its boggling chic. Anything to be "far out." No one wants to call this pretentious nonsense or to be caught missing what cautious minds judge just might be ordinary behavior a few years hence. The world may be getting madder, but "The Emperor's New Clothes" remains a reliable parable.

The marvellous production was "Beginner's Luck," created by Boston's Reality Theater. It will be repeated Wednesday through Saturday evenings at 8 and Saturday and Sunday afternoons at 3 in the YMCA, 24 W. Franklin St.

Here Jon Lipsky dramatizes the rise and fall of King Saul and the appearance of King David, inspired by his perceptions of the first Book of Samuel, who serves both as character and a narrator. The theme is power and how the devious can use an ordinary man, in this case Saul, to front for force and pride. This is an arresting view of the ancient story. Striking ideas sparkle, and Lipsky's rich vocabulary is always clear and arresting. The play's construction is complex but adroit and the music by Suzanne Baxtresser and Joyce Rosen contributes.

In striving for all the ramifications of the Saul-David relationships, Lipsky does bog down a bit, and I would hope for a tighter ending of his absorbing story. The striking production is under Vincent Murphy's direction in a set for which Charles Belardinelli relies effectively on burlap and sand. Tim McDonough is absolutely superb as Saul.So is Baxtresser as David. Phoebe Barnes is a creative Ruth, but so are all seven in this ensemble.

Finally, unlike anywhere else, there was humor and wit in Lipsky's writing and in the performers. This is a splendid theater group indeed, and if you're in Saratoga Springs this summer, you'll find it at Skidmore College.

Schedules and tickets may be had in the booths on Mount Vernon Place. Highlights I've missed include Tokyo's Yoshi and Co., performing today and Saturday at 4 and 10 p.m. and Sunday at 2 p.m.; the Warsaw Mime Theater appears Thursday at 5 and 9 p.m., Friday at 9 p.m., Saturday at 4 p.m., and Sunday at 2 p.m.; the Atelier Theatre et Musique of Paris begins today at 7 p.m., repeating Friday at 4 and 10 p.m., Saturday at 1 and 7 p.m. and Sunday at 4 p.m.