Mexico's President Jose Lopez Portillo said yesterday after concluding two days of talks with President Carter that he is happy with the Carter adminstration's apparent willingness to normalize relations between the United States and Cuba.

"If the United States or Cuba require our good offices, we would be only too happy to make any effort in that regard," Lopez Portillo said, "but I don't think it will be necessary because there seems to be goodwill on both sides."

Carter said in Kansas City last Oct. 16 he saw no immediate prospect for normalizing relations with Cuba, and "I don't advocate that as a goal for our country in the foreseeable future."

But after Carter's Jan. 20 inauguration, Secretary of State Cyrus R. Vance made statements indicating Washington was thinking about talks.

At a news conference, the Mexican president said he also told Carter yesterday that unless Mexico is helped with its economic problems, the United States will continue to be flooded with illegal Mexican workers.

Mexicans comprise the bulk of an extimated 6 million illegal U.S. immigrants. "To the extent that Mexico restablishes its economic equilibrium, the problem wil be solved," Lopez Portillo said he told Carter.

The White House gave few specific details about yesterday's hour-and-15-minute meeting between the two newly elected Presidents.

White House press secretary Jody Powell said the talks were "full and friendly . . . useful and cordial," and quoted Carter as saying they "served to reaffirm the close, friendly and cooperative relationship between the two countries."

Carter sent to the Senate yesterday for ratification a treaty for exchanging prisoners between the two countries, signed in Mexico City on Nov. 25. There are an estimated 600 Americans in Mexican jails, most of them convicted of charged with smuggling drugs, and about twice that number of Mexican prisoners in U.S. jails, the White House said.

On other White House matters:

Powell said the White House and the Justice Department, "out of an abundance of caution," are checking the status of Pat Caddell, Carter's campaign pollster, and Jerry Rafshoon, his longtime media adviser, to see if their unpaid advice to the President makes them special federal employees.

Attorney General Griffin B. Bell said Monday that presidential confidant Charles Kirbo is subject to federal conflict-of-interest laws because under a strict, 14-year-old statute, he is a "special employee" of the government every time he advises the President.

Powell also urged homeowners and businessmen in areas that may face spring flood threats to rush out and buy federally-subsidized flood insurance at "bargain rates," because it "saves money in the long-run for taxpayers generally."

In an effort to improve relations with Congress, the White House is giving some thought to increasing the size of Carter's 16-person congressional liaison staff.

Powell said it is now smaller than it was under President Ford, but "there are a lot more Democrats for us to deal with than there were Republicans for them to deal with."