Mayor Kevin Faulconer, distance running champion Meb Keflezighi and 92-year-old marathoner Harriett Thompson are scheduled to take part in a kickoff ceremony this morning in the center's Hall B.
The expo is free and open to the public, taking place from 11 a.m. to 7 p.m. today and from 9 a.m. to 5 p.m. Saturday.
Saturday will also include the inaugural Rock 'n' Roll 5K, which begins at 7 a.m. at Sixth Avenue and Palm Street on the west side of Balboa Park.
The marathon will get going in the same area Sunday around 6 a.m. Keflezighi plans to compete on the half-marathon course. Last year, he served as a pace-setter for the 13.1-mile race.
The band O.A.R. will headline a post-race concert Sunday at Petco Park, beginning at 10:30 a.m.