It is Fiesta Week in San Antonio. People are jamming the streets celebrating the arrival of spring with parades, fireworks, carnivals and plenty to eat and drink.

No matter how spirited the festivities become, they will have a difficult time duplicating the excitement inside HemisFare Arena during Spurs basketball games.

San Antonio basketball fans enjoy a season-long fiesta with their beloved team. Four pure spirit, noise and, at times, rowdiness, no NBA crowd equals the ones here.

"This is maybe the hardest place in the league to play," said Butlet guard Kevin Grevey. "I know none of us loves coming here, it's loud and they really root for their team, and they're right on top of you."

Spurs' fans ring the court. They sit so close to the action that they can practically reach out and touch the players. They are uninhibited, cheer every move by the Spurs. Nothing the visiting team or the officials do is correct.

It's much like the crowd at a fight, the other sport San Antonio citizens relish. The rougher the action and the more physical the play, the louder the cheering.

Remarkable as the courtside scene is, the Spurs once wondered if they would have any fan support. It was considered a gamle to put a basketball franchise in a city that seemed to love only football, boxing and baseball.

"We've had to educate the fans here, no question about it," said Wayne Witt, public relations director been very bug in Texas, especially here. We had to make things attractive enough to interest them."

So the Spurs sold the idea of a family atmosphere. They kept ticket prices reasonable (their top ticket is-8) and talked about wives and children coming to the arena for whole some recreation.

It took time for this Southwest Texas city to embrace this concept, but once the club acquired Swen Nater and George Gervin during its 1973-74 inaugural season here, the once-failing franchise, which began it pro life as the Dallas Chaparrals, took off When the American Basketball Association folded, the Spurs were sound enough to be one of four teams to enter the NBA.

"The fans were unsophisticated about basketball, at first," said Witt "They didn't know what to cheer for. Now they do, and I think things aren't quite as noisy in the arena anymore."

But the fans haven't changed on long time habit, they still arrive late for games, sometimes not filling up the arena until halftime.

The Franchise is in the black financially and will be able to pay off its NBA entry fee this year if it goes fay enough in the playoffs. The original season ticket total of 500 has increased to more than 5,000, and interest is so high that another 6,000 seats are being added to the arena, raising capacity to 16,000 for next year.

Fans are so exicited about the Spurs current playoff series with the Bullets that a few stood in line for 12 hours Saturday to purchase the remaining standingroom tickets.

Eventually, the present 64 Spur owners hope to sell stock in the club, so more local residents can be involved in the franchise.

"They developed a love affair of the team," said Wit. "The gamble has turned into a success story."

The most obvious romance is between the players and self-labeled group, Baseline Bums, perhaps the most exclusive fan club in the NBA.

The Bums limit membership to 120, and they have a waiting list. The Bums aren't hard to pick out at games; all wear T-shirts hearing the name and all sit in a section located above the visiting team's locker room.

Before anyone can join the Bums, he is subjected to a series of interviews. Roll call is taken at every game and members with bad attendance are dropped. And the only thing asked of members, besides $15 in annual dues and the prices of season tickets, is enthusiasm.

Visiting players have objected to the taunts of fans. Kevin Porter once tried to take on a front-row patron who had been yelling at him. And Dave Cowens went into the stands after someone called him "a redheaded sissyy." It took a bunch of San Antonio policemen to restore order and get Cowens back on the court.

Yet visiting players enjoy coming to San Antonio. The climate is pleasant, the city is informal and friendly and the night life varied and interesting.

The center of San Antonio is its River Walk, a group of restaurants, bars and hotels built around the San Antonio river, which winds through the center of town. Nearby is the site of the 1968 Hemisfare, which celebrated the 250th anniversary of the city.

There is a struggle between the old and new here.On one city block a department store literally surrounds an olds mission church on three sides. The church has refused to move and conducts business as usual despite the intrusion of commercialism.

This city of almost a million people, 55 percent of whom are Spanish speaking, is 75 miles from Austin 200 miles from Houston and 150 miles from the Mexican border. It is an area of great wealth and poverty, surrounded by a ring of U.S. military installations.

"One of America's four unique cities." Will Rogers once said about San Antonio, with the Alamo as its main tourist attraction.

The Spurs reflect the city's informality. They are free and loose and Coach Doug Moe spends as much time playing golf as he does drawing X's and O's.

"It's a family oriented city," said Gervin. "The people are friendly and no one demands a lot from you. You can be yourself and nobody minds. "It's a great place to raise a family."

And, he added with a smile, "It's not a bad place anymore for a basketball team."