Two incumbents and four challengers have announced that they will run for the Falls Church City Council in the May 6 elections and are seeking support from the city's nonpartisan political group, Citizens for a Better City.

The terms of four council members expire June 30. Incumbents Gary Knight and Elizabeth Blystone have announced their plans to run for the seven-member panel. Knight, elected to the council in 1978, is completing his second full four-year term. Blystone, a 12-year School Board veteran, was appointed in 1984 by the council to fill the unexpired term of Elizabeth Cesnik, who resigned her position to move back to her native Wisconsin.

Vice Mayor Robert Hubbell announced in November that he would not seek a third term on the council. Hubbell was elected in 1978 and has served as vice mayor since 1980.

As of Tuesday evening, Mayor Carol DeLong had not said publicly whether she would run for a fourth council term. DeLong, elected to the council in 1974, has been mayor since 1980.

Three of the four new candidates are seeking election as a group: Sue Bachtel, Dan Robey and Ray Stewart. They say that they are dissatisfied with the council's decision to widen Broad Street and that the council has not been responsive enough to the majority of the citizens.

Cesnik -- now Elizabeth Havlik -- has returned from Wisconsin and is the fourth challenger on the ballot. Havlik, who served on the School Board for six years, was elected to the council in 1982.

Each of the six candidates is hoping to win one of the four nominations of Citizens for a Better City at its open nominating convention Feb. 12. Nomination by the 27-year-old group is considered an important campaign step the election.

Tom Carlin, president of the group, said one of the 250-member organization's chief functions is a nominating convention every two years before the spring City Council elections. Any Falls Church resident eligible to vote in the elections may vote at the nominating convention.

Stewart, a Falls Church lawyer, said he thinks most city residents opposed the council's decision to add a fifth lane to a half-mile stretch of Broad Street. Work on the project, approved by the council in September, is expected to begin in the summer of 1987.

"The widening will open up the city to more commuter traffic and leave little room for meaningful landscaping, while at the same time cut out precious parking, especially for small businesses that give Falls Church its small-town feeling," he said.

Said Bachtel, who heads the city's Village Preservation and Improvement Society: "We feel that many citizens oppose a series of recent land use decisions by the council that . . . will tend to destroy its urban village atmosphere . . . chew up its open space, and . . . invade its single-family-detached residential areas." .

Bachtel said she opposed a recent council decision to rezone a parcel of land on West Great Falls Street from single-family residential to town houses.

Robey, a Falls Church lawyer, said, "We are a small town of two square miles, and land use decisions like this leave little margin for error."

Blystone, who voted to approve the Broad Street project, defended the council's action.

"It was a good decision," she said. Blystone said widening the road at the western end of the city is necessary to keep traffic moving smoothly through the center of town and away from residential streets.

Havlik said she "had no argument with the council" on the decision.

The financial officer for the National Crime Prevention Council in the District, Havlik said the council must have good communication with Fairfax and Arlington county officials about development and transportation, particularly with the coming of Metro.

"We need to be careful in how we do our planning in relation to other jurisdictions," she said.

Knight said he thinks Falls Church must continue to attract business. "We must maintain our ability to attract the kind of moderate commercial growth we want," he said.

All six candidates agreed on the importance of the ongoing study of whether to move George Mason Junior-Senior High School to the less congested Whittier School site.

"As a minimum," said Knight, "we have to make access to the school by student pedestrians safer than it is now."

Stewart said he is not sure a move to Whittier is the answer. "I think there are some middle grounds we ought to really look at."

Falls Church residents interested in running for the council must file by March 4. Deadline for voter registration is April 5.