Curtis and Sarah Crolius, world travelers, bon vivants and music lovers, have found their own private Elderhostel right here in Salt Lake City _ the Temple Square concert series, where they never miss a show.

Winter residents of Englewood, Fla., the Croliuses have traveled the country and been to Europe 15 times, and they enthusiastically proclaim there is just no other place where you can find such a bargain in quality classical music.

"We would have to pay $20 a ticket to hear such music in Sarasota, and it's free here," said Curtis Crolius, a youthful octogenarian who stands 6 feet, 6 inches tall. "Incidentally, the concert people should put me on their payroll! Since we came here attendance has really increased. I meet people all over town and encourage them to come to the concerts."

These outgoing Southerners have become regular summer residents of Salt Lake City, coming for the past four years for lengthening periods. They love the people here, and the mountains of Utah. "Actually we have the same sort of mountains in Florida," Crolius guffawed, "It's just that all but a few peaks are under water!"

Despite the distance, they encourage friends from Florida to make Utah a destination and have had a good many such visitors. "Our friends the Leon Karels, both Ph.D.'s and retired teachers, were just here for a week and they loved it. They want to come again next year," said Sarah, whose wide smile lights a round, happy face like sunshine.

Though their means are quite limited in retirement, "we live about as well as anybody," said Curtis. "We have friends who are millionaires, and I don't see much difference in the quality of our lifestyles."

One thing that makes Utah possible is a very reasonable, furnished apartment, where they enjoy pool and jacuzzi, exercise and reception rooms. Dinner out is likely to be at McDonald's _ not just to save money, but so they won't eat too much.

The Croliuses didn't miss one Gina Ba-chauer concert in June (director Paul Pol-lei saw that they had season tickets, as unofficial Salt Lake boosters). They also go occasionally to Utah Symphony pops, they loved the youth show, "Prime Times" at Promised Valley Playhouse, and they attend all Mormon Tabernacle Choir practices and Sunday morning broadcasts. Noting their departure last year, conductor Jerold Ottley announced, "We're losing two of our people."

While here, they attend their own Methodist Church, and Crolius recently sang a solo at the Sunday service in the downtown First United Methodist Church. "I can't sing in church choir any more because my eyes are too poor _ only solos," he said with cheerful resignation.

Englewood is a town of 20,000, 30 miles south of Sarasota on the Gulf of Mexico. There the Croliuses own a seaside home, where they enjoy musical evenings in the long living room, and a hospitable flow of visitors through a guest room with its own entrance.

The couple hails from North Carolina, where Sarah worked as a district instructor for the telephone company in Greensboro before their marriage, and Curtis traveled the state as a paint salesman. They lived near Mocksville for many years, on a 118-acre family cattle farm that once belonged to Daniel Boone.

Curtis was a bass soloist in the Presbyterian Church for many years, both in Winston-Salem, N.C., and Sarasota, and "went the oratorio circuit," singing the solos in "Messiah," the Brahms Requiem, "Elijah," "St. Paul," the Mozart Requiem and many others. He also plays many instruments, including violin and piano, and organ every day before breakfast.

He likes to tell about how he sang at the Met _ as a boy soprano among a host of children in Mahler's Symphony of a Thousand, with Leopold Stokowsky conducting the Philadelphia Orchestra.

Both enjoy abundant good health. His only sickness was polio when he was 6: "It stunted my growth," he said with a big laugh. The disease destroyed the hearing in one ear, but that in no way diminishes his enjoyment of music.

The couple drives 2,600 miles to get here. Actually she drives, going "every possible way" to see the sights of America.

How did they discover Salt Lake City? Quite by accident, said Sarah.

"We were accustomed to going to Europe. We belonged to the Holland Sporting Club and another travel club, and we could fly into Amsterdam on KLM for as little as $235 round trip, when the dollar was so strong. We used to follow From-mer's `Europe on $5 a Day,' and we had wonderful experiences, all over Italy, Sicily, Germany, Holland, France, the Scandinavian countries and Finland. We traveled to China, including a 1,000-mile tour down the Yangtze River; we covered all of Japan." "We went to the Eisteddfod in Wales, just on a whim, and after much difficulty we found lodgings with a family named Short. The man was only five feet tall, and we made an odd couple!" laughed Crolius.

"Then it occurred to us that we always headed east across the water, sometimes twice a year, and we had never really seen our own country. We decided to look westward," said Sarah. "Our first trip was to Nova Scotia with Elderhostel, and to Prince Edward Island, and it was wonderful."

The second year, 1984, the pair looked for an Elderhostel that offered watercolors for her, to supplement her oil painting skill, and computers for him. They decided on La Grande, Ore., for the watercolors, though he had to settle for drama.

"On our way we stayed in Salt Lake City, and went to Temple Square," Sarah continued. "We loved it so much we lingered for a week, then went to La Grande for our three weeks of school. On our way back we spent another week here. In 1985 we decided to stay four weeks; the next year we stayed two months, the third, 2 1/2 months, and this year we are spending four months, from May 27 to Sept. 27."

To stay young and healthy, get out and do something, this zestful couple advises; and inventive thinking is much more important than money. "Many old people think so much about themselves, they never see what is all around them," they agreed.