Police officials will be closing Paseo Colón Saturday at noon in anticipation of the Festival de la Luz.
The program begins at 3 p.m. for a pre-festival for younger children.
For police the day starts at 6 a.m. as the first group of what will be 800 Fuerza Pública officers take to the streets.
Among other duties, officers will be guarding the elaborate floats that will be parked along the south side of Parque la Sabana.
Officials urged parade goers to leave the bulk of their money and possessions at home.
Bus travel, including some long-distance out-of-town routes will be affected. An area from La Sabana to Calle 11 and two blocks on each side of the parade route will be restricted.
The closings will affect the Circunvalación, the General Cañas highway and the Caldera highway which runs along the south side of the park.
Traffic officials said they would field 200 officers.
There also are contingents of fire fighters, Cruz Roja workers and even workers from the Patronato Nacional de la Infancia, the child protection agency.
Perhaps as many as 1 million spectators will attend. The route is from the park to the Plaza de la Democracia.
Those not willing to challenge the crowds for a good point of view will find the event televised by several stations.