A US delegation led by Secretary of State George Shultz was scheduled to arrive in Mexico for two days of talks. The talks will focus on the guerrilla wars in Central America and the possibility of trade concessions to Mexico, Western diplomats said. Both issues are sensitive. US intervention in Central America is not popular with either the government or people here. Yesterday, some 2,000 demonstrators marched through the capital's streets and demanded an end to US intervention in the region. Washington also recently wiped several Mexican goods off a list of preferential exports - raising duties at a time when Mexico's economy is under severe strain.