Now and then, they say, some middle-aged vacationer strolls in from the clutter of downtown San Diego's tattoo joints and abandoned massage parlors to gaze around the lobby of the unlovely old building at 500 W. Broadway.

"Just wanted to see if it's like it was," the visitor is apt to explain to no one in particular.

Well, it is and it isn't.

It is still unmistakably the Armed Services YMCA with its registration desk (rooms $6.50 a night, $7.60 with color TV), its food counter, its side room full of pool tables and its signs indicating the availability of barbering, laundering and lockers

There is the display of tinted photographs of uniformed sailors and marines and the small rack of paperback books and magazines.

But the extensive "ship's service" store has been reduced to a glass case containing a few toilet items-toothpaste, razors, shaving cream.

And there are no uniforms. That's the big thing. There are some young men around-obviously servicemen by the look of their haircuts-but they wear sports shirts and civilian trousers.

That's not the way it was in 1942-the early days of World War II-when Anna Mae Wright, Phyllis Mondoc and Athleen Bassett came to work at the Armed Services Y.

"It was going full steam around here 24 hours a day," recalls Ms. Mondoc, now secretary to Executive Director Howard E. Whitney. "There were servicemen sleeping on pool tables, on top of lockers, in phone booths . . . everywhere."

Ms Wright, now associate executive director, remembers:

"When you came to work at 7 a.m., you had to walk over all the bodies of boys sleeping. Sometimes there would be two or three inside a phone booth with the door closed so they wouldn't fall out."

And Ms. Bassett, now the business office manager, says:

"All I can remember is how crowded it was. We had a piano in the lobby and some of the boys would come in and play all afternoon . . . "

That was the overflow. Others were sleeping in the more than 300 beds upstairs, 100 cots set up nightly in the gymnasium, another 100 or so in adjacent Davidson Hall and perhaps 75 more in a Quonset hut over on F St.

In those days more than 20,000 young servicemen a day were going in and out of the building, looking for a place to telephone home or clean up or dance.

"They all seemed to gravitate here," Phyllis Mondoc said.

Art Rogers, a Los Angeles man who lived at the Y for two years at the beginning of the war, said he can remember when it wasn't so crowded.

Rogers, then an enlisted man assigned to 11th Naval District headquarters, actually began living at the Y months before Pearl Harbor.

"At first, we kind of had things to ourselves," he said. "I guess a lot of the guys who just wanted to go into town and booze it up never went near a YMCA, so we had pool tables and all those things without the crowd.

But it did not stay that way for long. "Within a couple of years, it was so loaded with guys, it was a madhouse," Rogers said.

And although there were rules of the sort one might anticipate at any YMCA, Rogers confessed, "We just had to sneak jugs in once in a while and have little parties in each others'rooms. You know, it was like being in a nice, big boarding house with the guys you worked with.

"Then once in a while they would have to post a notice on the bulletin board about the empty bottle showing up on the roof of the gymnasium.

But all in all, Rogers said, "it was a nice, inexpensive home away from home. The little restaurant served good, cheap meals and our rooms were always kept nice and clean for us."

And, he said, "I don't remember ever hearing of anything being stolen out of any of the rooms or of any real trouble or brawls."

Charles Waldecker, 54, now a civilian quality control specialist at Long Beach Naval Shipyard, was stationed at the old destroyer base here during the early part of World War II and "used to hang out at the Y all the time."

It was,said Waldecker, who spent 20 years in the Navy, "one of the better places for a service person to hang out. What I really remember was that machine where you put a nickel in and got a big, cold apple."

He remembers, too, the sadness of the first wartime Christmas.

"Everybody was sitting around thinking of home while they played Christmas songs. The war had just started . . . "

One San Diego old-timer is Sam Halum, 64, president of the Fleet Reserve Association and manager of the Bachelor Officers Quarters at the Naval Station.

Hallum retired from the Naval in 1962 as master chief commissaryman after a 30 years tour.

In 1932, he was stationed abroad the old light criuser Raleigh, moored in San Diego Bay beyond Broadway Pier.

"We couldn't get out to the ship after the boats quit running at midnight, "Hallum recalled. "Guys would go the Y where you could stay overnight for 50 cents-but a lot of them would'nt have the 50 cents so they'd just sleep on the floor in the lobby."

These days, Executive Director Whitney said, the average daily attendance is still about 3,500. But it is estimated that more than 128 million persons have walked through the front doors since the building opened in 1924.

In 1934, the fleet was sent to the East Coast for eight months. There was no one around. On one occasion, an executive went to the lobby to greet a single serviceman who had wandered in. On another, the only entry in the financial log was a $4.50 refund.

The place survived and when World War II came along, the Armed Services Y took over operation of a USO club in Davidson Hall, a connecting former repair garage acquired by the federal government. In 1946, Davidson Hall was purchased by the Y for $65,000 to become a recreation room for dances, stage shows and other events.

But the war was over and gradually the place changed.

Today, the swimming pool is empty (local bases have their own) and servicemen coming to town are looking for other forms of recreation, Whitney says.

The gymnasium-also replaced by similar facilities at bases -has been turned into a room full of slot-car race track and pinball machines-which produce approximately $1,000 a month in revenue.

With servicemen now allowed to go to and from ships and bases in civilian clothes, the demand for lockers is minimal. The Y once had 1,100 of them. There are now about 400, of which only half are in use.

One of those has been assigned for at least 25 years to a man who faithfully sends in his rental fee from various parts of the world. As far as the staff knows, he never comes around to look inside.

The Armed Services YMCA manages to make enough off its services, room rentals, lunch counter and the like to be more than 90 percent self-supporting, Whitney says. The United Way allocates enough for about 6 percent of its budget.

The Y is reaching out more and more from the tattered neighborhood it currently inhabits, putting on recreational and other programs in Navy housing areas around San Diego.

That follows a tradition set in World War II when Fahy Johnson developed an entertainment troupe that hit all the local bases and in the postwar years when the Y operated a camp for Navy families near Julian.

But none of it has ever again resembled those days during the big war when, as Phyllis Mondoc recalls, one floor was entirely taken over by an Army unit that kept the jukebox going constantly and "it was just chaos."

When, as Athleen Bassett remembers, "All you would see was a sea of blue uniforms . . . On weekends, the place would be packed with men singing."

Or when, as she and Anna Mae Wright recall, a young Navy officer walked in, saw the young woman working at the room desk and said, "That's the woman I'm going to marry." And he did.

"Oh, we've had a lot of romances," Ms. Bassett says. "A lot of the girls who worked in the soda fountain met their husbands here."