Albert C. Eisenberg, long active in Arlington civic and Democratic Party activities, announced yesterday that he will run for one of the two County Board seats to be contested in the fall election, but left open the question of whether he would run as an independent or a party nominee.

Eisenberg, 36, is the first candidate to announce he will oppose the board's two Republican-endorsed independents, Walter L. Frankland Jr. and Dorothy T. Grotos, whose terms expire this year. Neither of the eight-year incumbents has announced reelection plans.

Yesterday Eisenberg criticized what he called the Republicans' "misguided political appointments to the School Board which have eroded public confidence in the leadership of our school system, their cavalier approach to tax and fiscal policies" and their "extreme budget proposals which would strike at the heart of county services."

He said Republican attempts to cut the tax rate last week would have led to unnecessary reductions in services, and contended a current controversy over the performance of school Superintendent Charles E. Nunley could be directly traced to the Republicans' school board appointments.

Eisenberg, who is married to Sharon Davis, chairwoman of the Arlington Democratic Committee, was accompanied by about two dozen supporters, including Richard Buffum, who is expected to announce his County Board candidacy soon.

Eisenberg, director of government affairs for the American Institute of Architects, said economic development should not be allowed to encroach on residential communities, small businesses must be retained, the housing crisis resolved and Metro made more cost-effective.

He is a former staff director of the U.S. Senate Housing and Urban Affairs subcommittee and a past chairman of the Arlington tenant-landlord commission.