President Reagan said yesterday that he is intrigued by a proposal that the Mexerican-American border be opened to free movement by the citizens of both countries and that Mexicans currently in the United States illegally be given the right to remain.

Reagan said he would discuss this proposal with Mexican President Jose Lopez Portillo when they next meet in late April.

Reagan said that Mexico's unemployment rate creates pressures for which immigration to the United States is a vital "safety valve."

"It is to our government's interest also that that safety valve is not shut off" so that there is no "breaking of the stability south of the border," Reagan told Walter Cronkite in an hour-long interview broadcast last night by CBS.

In addition, if immigrants had legal status, U.S. employers could not take advantage of them and the U.S. Treasury would benefit from their taxes, Reagan said.

"They would be able to legally back across the border if they wanted to, and come back across, but the border would become a two-way border for all our people," Reagan said in describing the proposal that has been suggested by governors of U.S. and Mexican border states.

On foreign policy questions, the president told Cronkite that one obstacle to a Soviet-American summit might be removed if the Soviets indicated they would eventually withdraw their troops from Afghanistan.

He also said that there is no parallel between El Salvador today and Vietnam in the early 1960s, but that it is important to draw the line against communist activity because "it isn't just going to stop at El Salvador. We know that there are evidence of this."

Reagan said that he only learned after the fact of one of his administration's first moves against the Soviet Union. He said that he had no advance word that the State Department had decided to withdraw Soviet Ambassador Anatoliy Dobrynin's privilege of riding in his limousine directly into the State Department building.