Every racetrack community is filled with people harboring dreams of the future. They work as ushers, mutuel employes, parking lot attendants, but they see the job as a way of paying bills until they get their break and succeed as a trainer, jockey or owner.

Kenny Masters was one of them. While he aspired to become a trainer, he worked in the mornings as an assistant trainer and in the afternoons as a valet parking attendant at the three Florida tracks. "It got pretty frustrating," he conceded.

Masters had had a successful career as a minor-league jockey, principally at Waterford Park in West Virginia. He rode his last race here, at Calder Race Course and then said, "I put out the word that I was looking for a training position. I thought by working as a valet parker I'd have a chance to meet people, and I didn't have anything else to do in the afternoons anyway. I had a couple deals that were supposed to happen but they didn't. So I kept on working and hoping that something would happen."

In those tough days last fall, Masters would gladly have settled for a job training a few modest claiming horses. He could not have imagined that he would be saddling one of the favorites in a $250,000 race, but that is what he will do when he sends Mo Exception into Saturday's Gulfstream Park Handicap.

Mo Exception had been trained for most of his career by the man who bred him, Ken Kleier, but when Kleier decided this fall that he needed to devote full time to the management of his farm, he met Masters and hired him.

For the ex-jockey, this was fortuitous timing. Not only did the job enable him to escape the parking lot, but Mo Exception was just rounding into form after suffering from a virus.

Mo Exception won a couple of stakes at Calder in the fall, encouraging Masters to take a long shot flyer at Gulfstream. He entered the 4-year-old in the Donn Handicap against some of the biggest names of his generation, including Time for a Change, Dr. Carter and Key to the Moon.

Mo Exception's odds were 53 to 1, but he mocked the tote board when he shot past the leaders on the turn and scored the most stunning upset of the 1985 racing season.

Masters professed no surprise. "I thought he had a heck of a shot," the ex-jockey said, "because he's such a consistent horse." But most racing people looked on Mo Exception's victory as something of a fluke, and that view is reflected by the morning line for Saturday's Gulfstream Park Handicap.

Mo Exception is listed at 6 to 1, a longer price than all three of the big-name rivals he beat soundly in the Donn. Most horsemen think Time For a Change is the one to beat, having needed the conditioning he got from his last race.

Masters disputes this notion. "I didn't feel the Donn was a fluke," he said. "He won too easily for it to be a fluke."

Whatever happens, however, Masters already has established himself solidly as a capable trainer. Unlike most of the racetrack people whose pursuit of their dreams is a futile one, he has escaped the parking lot forever.