From the port, you can take #1 tram or #152 bus to Porta Nolana train station.
See http://www.anm.it/Upload/RES/PDF/LINEE/linea%201.pdf and http://www.anm.it/Upload/RES/PDF/LINEE/linea%20152.pdf

Take the train to Ercolano Scavi. From here there are a couple of choices to reach the 1000m car park/entrance. There is a scheduled bus service about once an hour which takes an hour to get there. There will also be a driver assembling a small group for a minibus trip, which is what we did. The advantage was that we would get back by about 1.00 pm. leaving time for a visit to Herculaneum, which is only about 10 mins walk away. They dropped us off right at the entrance. The drawback was that we only had 40 minutes or so to walk up, look round and come back down. Not really enough time to appreciate one of the earth's most famous features. Next time we'll go by bus.
Best wishes
Peter.

Many thanks Peter
Think we'll try the bus option - really looking forward to it.
How was the walk up? One of our party does not like heights!
Ciao

I don't think your companion will have any trouble. You don't have to have a head for heights as there is a fairly wide track up to the crater.
Regards
Peter.

Great, can relax a bit now.

Thanks again Peter

Cheers
Gillie

Don't forget to wear suitable shoes, because walking on lava is on a very rough surface and sandals may not be up to the job!

I have just come across this site http://www.vesuvianamobilita.it/orari/vesuvio/napoli-vesuvio.htm . It gives times of buses from Naples port, Molo Beverello, to Vesuvius. This would be much more convenient.
Best wishes
Peter.

Thank you both.
Really looking forward to some sunshine.

Cheers
Gillie