When searching for information about a university, your best bet is to first contact the 'Secretaría de Extensión Universitaria y Bienestar Estudiantil' or the Department of International Relations department at the university.
Typically registration for undergraduates is between mid-November and mid-December, though check with the university for exact dates; contact the 'Vicerrectoría Académica' or the department of admissions and registration.