GEORGE TOWN, Cayman Islands — Minnesota-based Mayo Clinic is opening a referral office in this western Caribbean city. The office will be a feeder for Mayo operations in London and in Arizona. Florida and Minnesota. Staff will assist patients with travel and lodging needs. This is the third Mayo office in the Caribbean to address “serious, complex and unsolved medical needs,” said Rafael Sierra, an orthopedic surgeon who is Mayo’s medical director for the Americas.