The Prince George's County Senior Youth Orchestra and Honors Chorus will perform for the third year in the Kennedy Center Concert Hall at 8:30 p.m. Sunday. Led by guest conductor Norman Scribner, the young musicians will play selections by Gershwin, Bernstein, Tchaikovsky and Gabrieli.

Leonard Bernstein and Aaron Copland, two of the composers whose works will be performed, are honorary patrons for the concert.

Tickets are available at the concert hall box office or by calling 345-8763.

A forthcoming Rockville Arts Division project will turn a thousand feet of construction fence into a sidewalk art gallery.

The division is inviting artists and community groups to decorate the fence, which will be erected at the site of the future Montgomery County office building and courthouse complex near Rockville Mall. Businessmen will supply needed materials, including the plywood panels that will be attached to the fence after painting. The panels are being used so that artists of all ages can paint indoors in comfort and safety. Applications must be in by March 7. For more details call 424-8000, ext. 305.

A reception from 2 p.m. to 5 p.m. Sunday will open a two-week exhibit of sculpture models and drawings submitted with the city of Rockville's application for a Works-in-Public-Places grant from the National Endowment for the Arts (NEA) grant. The reception, in the Municipal Art Gallery, will be open to the public. The sculptors will participate in a question-and-answer session, also open to the public, at 2 p.m. Feb. 26 in the Rockville Civic Center auditorium.

Government Services Savings and Loan in Bethesda has donated office space at 4733 Bethesda Ave. to the Montgomery County Arts Council. The council, which has been making do with a corner in the county arts division offices, plans to move to its new quarters by March 1 and is looking for donations of office furniture - everything from typewriters to desks and filing cabinets.

The council also needs volunteers for several projects, including its first newsletter. The deadline for arts organizations to send in information for the first newsletter, which will cover March through May, is Wednesday. To contact the Arts Council call Nancy Boskoff at 468-4172.

Free poetry readings are held at 8 p.m. on the last Thursday of each month in last Thursday of each month in the Kensington Park Library, 4201 Knowles Ave. The year-round program, which received a $2,000 NEA grant in 1977, is entering its second year. In addition to the Thursday night readings there are open readings, at which anyone - and the age range thus far has been from 4 to 85 - may read poems. The next open session will be in March. For details call Joyce Eminhizer at 949-4100.

Another event scheduled for the Kensington Park Library is a free concert by the Montgomery County Jazz Guitar Ensemble. It is set for 7:30 p.m. Monday. Sponsored by the recreation department, the program is part of the year-round free concert series which feature a variety of musical groups at various locations in the county. To be put on the mailing list, write Free Concerts, Bushey Drive Elementary School, 12210 Bushey Dr., Silver Spring, Md. 20902.

A new organization for dance audiences is Dance Affiliates, which was recently formed by the Dance Committee of the Jewish Community Center of Greater Washington. Members receive group rates for dance events, information about dance lectures, rehearsals and a dance film program. For details call 881-0100, ext. 46 or 66.

The Prince George's County arts division, helped by a grant from the Maryland Arts Council, will offer a series of three master classes in dance beginning Feb. 19 with the Washington dancer and choreographer, Jan Van Dyke. The classes, to be held at the University of Maryland's dance department, will include a beginning and advanced sections. For details call 277-2200, ext. 397.

Throughout February, Prince George's County artists will offer a series of lecture demonstrations at the Watkins Nature-Culture Center in Largo. Topics include preparation of surfaces for oil painting and drawing from nature. On Feb. 18 a special workshop will be held for children 12 and under. For details call 249-6202.

The Prince George's County arts division recently announced that for the third year in a row it has received an NEA Expansion Arts Program grant for its neighborhood arts programs. The $12.500 grant will be used to continue a bi-montly arts calendar and to offer a series of workshops. The first workshop, Career Building in the Arts, will be held April 1. For information call 277-2200, ext. 392 or 362.