LA JOLLA, CALIF. -- For decades, southern California college students have been driving to Mexico for carefree spring weekends, drink and sun and perhaps a little mischief.

From this eucalyptus-studded campus of the University of California, San Diego (UCSD), quite a different kind of movement to Mexico is under way. Students from here and two other local universities have been driving to Tijuana to build houses for poor families, part of a new student-volunteer movement seen on many campuses as a politically potent shift in the social consciousness of American youth.

Next spring, for the first time in a major U.S. city, all seniors in Atlanta's public high schools will have performed a required 75 hours of community service. ACTION, the federal agency, is funding an effort to organize all Minnesota colleges into a mass movement of student volunteers. The Campus Outreach Opportunity League (COOL), a Washington-based group begun by two recent college graduates, is advising student volunteer programs in 300 colleges.

And in California, the state legislature appears close to passing a bill for a "Human Corps," which would make community service an expected part of every public university student's education. The bill has given focus to a nationwide debate on whether public service should be a required part of every school's curriculum.

"Students are beginning to realize that they can't satisfy all their needs in life if they just go for the high salary, the BMW, the house on the hill," said Randon E. Woodard, director of student government and organizations' support services at UCSD. Several community service promoters suggest the new interest has a political dimension, since it reflects an urge to help welfare and education programs that -- in a time of high budget deficits -- have failed to get government money.

"I think a lot of really decent people are really becoming aware of a deterioration in the prospects for the future," said James Kielsmeier, University of Minnesota youth studies professor and national director of the National Youth Leadership Council. Minnesota's attempts to institute student volunteerism have been strongly supported by two leading Democrats, Minneapolis Mayor Donald M. Fraser and state Attorney General Hubert H. Humphrey III.

In California alone, the surge of student interest in volunteer work has led some experts to anticipate an increase of 100,000 to 400,000 in the number of available community workers, and brought several dozen community planners to a Stanford University Law School conference this month to plan for the deluge.

"I think the pendulum swings on a certain timetable," said Robert Choate, a 62-year-old San Francisco businessman who is credited for much of the new student interest in volunteerism in the West. As organizer of the California Coalition on University-Community Services, he helped set up the Stanford conference and also was the catalyst for last fall's upsurge in student community service in San Diego.

"Last year Bob Choate just called and asked if I might want to get a student volunteer office started," said Ellen Caprio, a recent University of California graduate who helped organize the Volunteer Connection on the campus here. At a volunteer fair in November, the first ever here, 150 students signed up for house-building projects in Mexico and tutoring jobs in disadvantaged San Diego schools. With Choate's encouragement, the group joined with similar groups at San Diego State University and the private University of San Diego to find suitable community projects and to poll volunteers on their good and bad experiences.

Volunteer activists have wondered for several months how their efforts might be affected by a proposal by Assemblyman John Vasconcellos (D-San Jose) to mandate public service for every student enrolled at a state university campus. The bill originally was interpreted as requiring volunteer work for graduation, but to aid its passage Vasconcellos added language encouraging, but not requiring, volunteer work.

Private secondary schools nationwide for years have encouraged voluntary public service by their students, who often have had little first-hand contact with poverty or other deprivation. A survey by the National Association of Independent Schools, however, indicates a recent surge in the number of private schools requiring community service for graduation. Of 277 association members who said they had community service programs, 49 percent had been in operation five years or less and 41.4 percent required students to participate.

In the Washington area, the Sidwell Friends School in 1981 announced it would require a 30-hour community service project for graduation, and the Georgetown Day School instituted a 60-hour community service requirement in 1983.

Mary Ellen Saterlie, associate superintendent for instruction for the Baltimore County schools, said her office has encouraged service projects at all 148 schools, but a proposal to require such activity throughout Maryland failed to win approval two years ago.

In Atlanta, Assistant Superintendent Barbara Whitaker said the city's new requirement of 75 hours service for high school graduation has inspired "no more than the usual teen-age complaints." Whitaker said other school districts have called to ask about the program, which requires students to present signed proof of their activity and write a 500-word essay on the experience. The program began in 1984 and applied only to incoming students, 5,000 of which are expected to graduate in 1988.

"Personally, I don't think it's necessary to make it mandatory," said Robert Hackett, 26, codirector of COOL. "We have found that students always respond, and lots of them." COOL's work coordinating campus volunteer activity began three years ago after codirector Wayne Meisel, 28, visited 70 campuses throughout the Northeast during a 1984 walk from Maine to the District of Columbia.

Cathryn Berger Kaye, youth leadership program director for the Constitutional Rights Foundation, has been coordinating community service clubs in 22 Los Angeles high schools for three years under a $200,000 annual Ford Foundation grant. At first, she said, she also opposed making the program mandatory, but now wonders if making it part of the curriculum might send the important message that community service is at least as important as physical education or algebra.

Choate said a mandatory program makes some sense at the high school level, because students that age "would not be offended, as college students would be, with menial or clerical chores." A university student, he said, will not stay with a project more than a week if he or she does not think the work is meaningful, and his programs emphasize careful review of the work that volunteers do.

Libby Gillingham, a University of California, San Diego junior and director of the Volunteer Connection, said that her group sends a questionnaire to volunteers asking how they rate the work and the experience. As a member of Delta Gamma sorority, Gillingham has been trying to lure the 9 percent of the university's 14,000 undergraduates who belong to fraternities and sororities.

The most difficult hurdle to overcome, she and Caprio said, is the academic pressure on students. High costs also have forced many to take jobs, which further reduce the time available for volunteer work.

Tom Tucker, assistant vice chancellor for undergraduate affairs at the San Diego campus, said he has been careful to leave the volunteer organizing to students and to bar creation of any university bureaucracy to oversee the effort. A recent survey indicates an unexpectedly large amount of student effort.

The survey reported a minimum of 22,917 student hours in public service in the past year, including 45 programs that provide no academic credit and 58 that do.

The growth in the number of student volunteers is so great, Choate said, that he thinks only the schools can absorb them, in the role of remedial tutors and instructors in overcrowded English language classes for adult immigrants. Nonprofit organizations are not going to be able to find enough work for them, he said, "until they totally revamp their approach."