There will be regular bus service to and from downtown during the two days of the G20 Summit. Vehicular traffic will be restricted and only buses, cabs and delivery vehicles will be permitted in downtown. No vehicles will be permitted in the four-block security zone surrounding the convention center. Buses are scheduled to run on weekday schedules; however, Port Authority warns that you should expect delays. Port Authority has posted alternative route maps on their website, outlining how buses will be funneled into downtown Pittsburgh during the G20 Summit. You can get a thumbnail of the routes in downtown on this interactive map. There are also overviews for how many of the buses will be affected. You can download information on individual routes here. By the way, according to the list released by Port Authority, the 54C, which directly services Polish Hill, will not have any route or schedule changes. Staffski recommends that you still allow extra time in your schedule if you are using the 54C. It sounds like there will be a lot of disruptions to traffic during the two days of the summit.
The route changes are only in affect on September 24 and 25. Lead up and post event routes and schedules will remain the same.