I don't think it'd be hard to navigate from Dobbins if GHP closed the roads for the motorcade. I was going home northbound on I-75 a few years back when W was heading from Dobbins south on 75 to somewhere north of the connector, and GHP had sort of a rolling blockage to escort the motorcade. However, getting from Dobbins down to the south side would be disruptive on a much larger scale, so ATL likely is more sensible. Hopefully they don't have to wait for a gate at ATL