The host city for this weekend's Group of 20 summit is preparing for an invasion of world leaders, police and protesters by shutting its doors. The Toronto Blue Jays baseball team is leaving town, the Royal Alexandra Theatre is closing for the first time in more than a century, and thousands of bankers and money managers such as David Cockfield are working from home. People coming to cover the G-20 are going to find Toronto just empty, with wind blowing through the downtown canyons, asking 'Where are all the people?' " said Cockfield, a portfolio manager at MacNicol & Associates Asset Management. A 12-block section of Toronto's financial district already is surrounded by 10-foot-high chain-link fences and concrete barriers, part of the largest security operation ever in Canada with 20,000 police and security guards.