The Central Intelligence Agency, an entity so secret that it won't reveal its budget or say how many people it employs, has been trying to get along with its neighbors.

Last week, as part of that effort, a 17-member citizen advisory committee, which keeps the intelligence agency informed of the views of its suburban Virginia neighbors, held a public meeting at Langley High School to review the CIA's $2.3 million plan to lessen traffic congestion on Dolley Madison Boulevard (Rte. 123).

The work, to be paid for by the CIA, will include the installation of two traffic signals on Dolley Madison -- one at its intersection with Georgetown Pike (Rte. 193) and the other at the entrance to the CIA's Langley headquarters complex.

Dolley Madison Boulevard's eastbound lanes will be shifted slightly between Potomac School Road and Merchant Lane to create a buffer between highway traffic and two nearby subdivisions, Evermay and Clearview Manor.

About 50 residents turned out for the meeting, and some said they believed that highway improvements would not be needed, particularly if CIA commuters make more use of the George Washington Memorial Parkway.

Engineers from a consulting firm hired by the CIA said that not all agency commuters use the parkway because other approaches, such as Dolley Madison, are more convenient.

The work has the approval of the Virginia Department of Highways and Transportation and is scheduled to be finished by 1987.

The highway improvements are being made to accommodate the increased traffic that a major expansion of the CIA's complex is expected to generate.

The expansion, which began last year and is projected to cost $179 million, will shift about 3,000 CIA workers now in offices elsewhere to Langley by late 1988, and those 3,000 are expected to commute in 1,000 cars.

The agency has pledged to add 1,000 parking spaces to the 5,000 it already has. (It is understood that the existence of 5,000 parking spaces there does not necessarily imply that each is occupied by a car used by three CIA employes, and that therefore current employment at CIA headquarters is 15,000. The CIA still prides itself on having secrets.)

The agency also is hiring a consultant to study ways of keeping rush-hour traffic at current levels, said Robert McGraw, chief of the CIA's new building project office, who attended the meeting.

The CIA plans to ask for $500,000 in its fiscal 1987 budget to build a new lane along a mile-long stretch of the northbound Capital Beltway, connecting Georgetown Pike to the George Washington Memorial Parkway.

One traffic improvement project is expected to be finished in late summer, McGraw said. It is a 1,000-foot acceleration lane, costing $960,000, running west from the CIA's exit ramp onto the George Washington Memorial Parkway.

CIA representatives have been working for the past 18 months with McLean area residents, as well as state and local officials, to develop a traffic management plan for the area.

Although McGraw said the CIA prefers a low profile ("We'd rather just keep our secrets"), he said the agency's traffic improvement plans necessitate public contact.

"The entire project has been pretty much up-front from the very conception," he said, "and I guess in the true sense of the word we consider ourselves neighbors."