Is'nt May 1st labor day? I am traveling from Naples Airport to Positano. Could there be any issues with the trip from the airport to Sorrento and then the bus system to Positano because of the holiday?
It is somewhat similar but don't know the degree it is observed. We have been in Italy several times over May 1st and never noticed anything different. Maybe the crowds were a little larger but we were not bothered at all.
Some transportation might run on holiday schedules, but to your locations there will be plenty of options.
Local transportation has a special holiday schedule, for example in Milan it runs until 7 pm, museums will be closed, as well as some shops. There can also be workers manifestations.