Members of performing arts groups in Arlington are waiting like nervous tryouts for a Broadway production to hear whether they will finally get their chance at the big time.

They are excited by what Elizabeth Weihe, president of the Arlington Visitors Commission, calls "a once-in-a-lifetime opportunity," the possibility that Arlington could get its own performing arts center. It would be part of the huge shopping mall to be built this year at Pentagon City, off Shirley Highway.

But not everyone is as eager as Weihe is about the project. On Feb. 23, the Arlington County Board is scheduled to decide whether to include a professional-quality performing arts center in the mall.

The developer of the mall, Melvin Simon & Associates of Indianapolis, had offered to contribute $5 million toward the projected $5.75 million cost of a 1,200-seat theater, which would be operated and controlled by the county.

A few weeks ago, the offer was withdrawn after the county and the developer agreed that Arlington no longer would help finance a $40 million garage for the mall, as once planned. Negotiations are under way for the county to pick up all or part of the $5.75 million tab for the arts center, county staff member Ron Carlee said.

That has left some members of the County Board nervous about the project. "It's certainly an exciting idea," said Chairman John G. Milliken. "But I have yet to be convinced it's something the community really desires and something we can financially handle."

Like many community cultural centers, the Arlington center's operating costs would have to be subsidized by the county in perpetuity, studies show. The anticipated subsidy varies from $325,000 a year estimated by the county staff, to the $229,000 projected by a consultant.

As a result, many county residents question whether Arlington should take on the project when performing arts facilities exist just across the Potomac River and at a time when proposed cuts in federal aid might require the county to subsidize more pressing community needs. They also question whether subsidy estimates are on target.

Supporters will present their arguments at a public hearing at 7:30 tonight at the George Mason University Law Center.

"There seems to be a real genuine excitement about the possibility of this project," said Theresa Furey, president of the Arlington Arts Advocacy Council, a group of 13 arts organizations. "It would be the first facility built specifically for the performing arts in Arlington. Right now, almost everything that's done is done in schools, which really aren't equipped."

Carlee said studies show that at least $12 million would be required to buy land and build an arts center elsewhere in the county.

County Board members Ellen M. Bozman and Mary Margaret Whipple are among the center's enthusiastic supporters. They argue that the county already subsidizes such county services as sports and recreation programs. Furthermore, they contend, anticipated losses would be offset by the projected $7.5 million in taxes the shopping mall is expected to yield annually. Private endowment funds and community fund-raisers also could reduce costs, they note.

"Having an Arlington showcase would just add so much to the community," Bozman said. "It's not that it's more important than anything else, but it's one thing which would help make us a full community . . . instead of thinking of ourselves as a bedroom community all the time."

Whipple says the proposed center would be different from arts facilities in Washington because it would be designed with local groups in mind, with tickets more affordable for families. Rather than featuring major Broadway productions, the Arlington center probably would attract smaller productions, studies show.

The County Board's other three members say they have not made up their minds. Board members Michael E. Brunner and Albert C. Eisenberg express concern that annual subsidies for the center might mean less money for other programs.

"It's not a high enough priority for me to push aside schools and police and fire protection and mental health programs, if it came to that," Brunner said.

"Is it the kind of thing we want to allocate money to on a long-term basis while other needs go unmet . . . and what if the whole thing goes sour and we're left holding the bag?" Eisenberg asked. "What gives me pause is that the [financial] studies could be way off base.