You might, and I stress might actually hear a SS agent talking with a local PD or SO unit. Just maybe...and it might be on simplex, so you would have to be close. Best bet is to monitor your local tac and little used local channels, for updates on the motorcade, arrivals and departures, etc. And YES do monitor the tower freq, both the VHF and UHF posted frequencies. I once heard the pilot call ground control as SAM 2700 as he wanted to re-position to the runup area at the end of the runway. Obviously, POTUS was not onboard...then heard the local PD say the motorcade had arrived at the airport, then the pilot contacted the tower as AF-1 and moments little it rumbled over my house. About as close to a complete comms exchange as you are liable to get.