More than 150 nations, including the Soviet Union, said they will attend the 1988 Summer Olympics in Seoul, according to a document received by the International Olympic Committee in Mexico City.

The document was signed by representatives of the nations attending the General Assembly of National Olympic Committees. Despite the signatures, one member of the IOC said, "There always exists the possibility that when the time arrives, some countries may decide not to go to Seoul, arguing, for example, that there are not sufficient guarantees for their athletes" . . .

In Seoul, the Seoul Olympic Organizing Committee, facing the loss of millions of dollars in television revenue, said several finals in the 1988 Olympics will be held during the morning hours to accomodate American viewers.

The SOOC said that boxing and basketball finals and one-third of the finals in track and field, swimming and gymnastics would be held at 11 a.m. local time, or 9 p.m. EST . . .

Jeff Blatnick, who won a wrestling gold medal in the 1984 Games, will accept the Touchdown Club's Gene Brito Memorial Achievement Award at a Tuesday luncheon at 12:15. Blatnick contracted Hodgkin's disease two years ago but came back to win the gold in the Greco-Roman super heavyweight division at last summer's Olympics.