Closest airport is Naples from where (I think) you could get a train to Salerno and a bus onwards to wherever you're staying (not sure whether you mean the Amalfi Coast in general or Amalfi town in particular. Positano is a beautiful town.
It can be very hot there in mid-Summer so May/June or September might be the best times if don't like too much heat. Also, it's less busy so easier/cheaper to get accommodation.
Beautiful part of the country with stunning views although you wouldn't want to have vertigo driving the coast road.