The May Day 2008 marches and rallies are underway and thousands of people have converged on downtown LA:You can expect massive traffic troubles through downtown during Thursday's events. Marchers will stage at 7th Street and Parkview at MacArthur Park, Olympic and Broadway, and Alameda and Central. All will converge at 1st Street and Broadway for a rally that is scheduled to start at 4 p.m. -- ABC7See our May Day Travel Guide for tips on......