Lee,
The Second Avenue overpass is the easiest location to see the operations. You can also see the arriving tug and car float from the public area on the 58th Street Pier.
Other areas are inside the Brooklyn Army Terminal, but they are located adjacent to NYPD facilities and are pretty much off limits.
Street running is along First Avenue from 58th Street to 39th Street (short section of private right of way through what's left of Bush Terminal Yard), viewable from public sidewalks
SIMS is switched as needed. Most trip leave in the morning to minimize vehicle interference along First Avenue, but they do make afternoon trips as well. Sims is next door to the Federal Detention Center at 29th Street and Second Avenue, so loitering is not encouraged.