The delegation is scheduled to meet Friday with activists and government and community leaders describe programs aimed at preventing violence and developing local economies.
An estimated 2.5 million Salvadorans already live in the United States.
The group has already visited Guatemala and plans to head to Honduras, as well as visiting migrant detention facilities in McAllen, Texas.
The Trump administration is trying to restrict applications for asylum in the U.S. from Central America by requiring migrants to apply in Guatemala rather than at the U.S. border.
Pelosi's delegation includes a dozen lawmakers, including the chairman of the House Foreign Affairs Committee.