SAO PAULO — Protesters and police clashed in Sao Paulo Thursday, as demonstrations against the World Cup and rallies calling for improved public services erupted in several Brazilian cities. Officers in Brazil's largest city fired tear gas and rubber bullets at protesters who set piles of trash alight to barricade a central avenue. Demonstrators blasted the billions spent to host next month's soccer tournament and said they wanted to draw attention to what they called a lack of investment to improve poor public services.