Ethel Merman has traveled all over the world both for her work and for pleasure. Her home is New York, but she is there at intervals: fit into a busy schedule like her current one -- it will take her to San Jose on Feb. 4, back to Manhattan on the 6th, to Florida for three concerts on the 14th, and then possibly out to the West Coast. "I like going wherever I'm invited," she says, "as long as the people are nice." Washington is one of her favorite places -- "It's always a good city to play in." She reopened the National Theater with "Call Me Madame" in the 1950s, and performed at the inaugural gala for President Reagan last year. Tonight she will be in Washington again, this time performing in the Washington Opera Gala at the Kennedy Center. Other favorites:

* Her hometown, New York: where she insists she leads an unglamorous life: "I go out to lunch, visit friends, shop." Every Wednesday, Merman does volunteer work at Roosevelt Hospital. In town, she never goes to Greenwich Village, preferring the upper East Side and "the same few restaurants all the time." She has adapted to being recognized on the street.

* London: "I love it. I just did a command performance before the Queen Mother of England. Nov. 8, a charity show. I've also played the Palladium, and the Talk of the Town dinner theater." She enjoys London's fine hotels and most recently stayed at the Connaught, although she also likes the Dorchester.

* Hong Kong: She has fond memories of the city and particularly of a world tour with her son in 1965. "That trip we also traveled from the top of India to the bottom, from New Delhi to Bombay."

* California: Although it is usually work that takes her there -- she will make the trip next month for a concert in San Jose -- she also feels at home in California. In Los Angeles she stays at the Beverly Hills Hotel. Recently she was there with her son, when she also visited the Catalina Islands.