No, Saúl Martínez was not a part of the 1998 World Cup. He was born in 1976, and was therefore only 22 years old at the time of the tournament. He had not yet established himself as a regular player for the Costa Rican national team, and was not selected for the squad that traveled to France.
The Rise and Victory of Saúl Martínez: A Legendary Honduran Footballer