About 20,000 walkers and runners are expected to hit the streets of San Diego this weekend for the 12th annual Rock-N-Roll Marathon.

More than 40 live bands and cheerleading squads will line the 26.2-mile course.

The race begins at Sixth Avenue and Palm Street near Balboa Park and ends at the Marine Corps Recruit Depot in Point Loma.

The only major freeway that will be closed is the southbound 163 between Interstate 805 and downtown.