President Reagan has signed documents designating his Santa Barbara County ranch as the Western White House and has planned a visit there Feb. 19, The Santa Barbara News-Press reported today.

Mr. Reagan plans a three-day stay, which would be the first since his inauguration.

Undisclosed sources in the Santa Barbara area and in the Secret Service confirmed the trip and the Western White House designation, the newspaper said.

It had been expected that Mr. Reagan would designate the ranch, which is 30 miles northwest of Santa Barbara, as his official residence outside Washington. However, a Federal law required him to sign documents so that Federal money could be used to provide the various facilities on the ranch that the President would require.