GOTG:
Nettuno I think is another name for the town where Paestum temples are located. The temples are fabulous and worthy of a separate trip from anywhere. Google Paestum and you'll find a trove of information. They were the highlight of our 10 trip to Amalfi coast.
We went to Paestum in October last year, and walked down to the seafront to locate the monument to the 36th Division who landed on that beach in WWII. It was off-season, but the seaside businesses were shuttered and it didn't really look like that much would be going on even in-season. I certainly could be wrong. You know how beach towns look in the off season! We didn't get a look at the beach, but Google Earth views make it look extensive.
There is a very nice, linen-tablecloth restaurant at the edge of the ruins site, Ristorante Nettuno, that had very good food (pricey). There appeared to be a number of small restaurants at the temple site, but we didn't try any. There is a hotel there that someone else on Fodor's reviewed, I think, and recommended.
It would definitely be different from Rome. I don't know how much help this is, but FWIW, I thought I'd offer our experience there.

From Wikipedia...

>>>> Paestum is the classical Roman name of a major Graeco-Roman city in the Campania region of Italy. It is located in the north of Cilento, near the coast about 85 km SE of Naples in the province of Salerno, and belongs to the commune of Capaccio, officially also named Capaccio-Paestum.>>>

By coincidence though, there's a road there called, "Via Nettuno" - which leads from the archaeological site to the coastal resort!

Gorgeous temples, but a bit far from Rome?

http://www.pbase.com/isolaverde/paestum

Somewhat closer is Sperlonga, which we liked enough to return to for a second stay! Should be doable as a daytrip - an hour by regional train to "Fondi Sperlonga" station, then about 10/15 mins by local bus....

http://www.pbase.com/isolaverde/slides_sperlonga

Stuff about Lazio in English is really hard to find!

Peter

Forget Nettuno and go to Sperlonga or Gaeta, both lovely seaside towns with great beaches and ambiance. If you want to delve into the WWII history stuff, go to Anzio and visit the museum (if you can find it and it's open) and the cemetery. Lovely towns, all three of them.

Nettuno and Paestum are not the same place.

If you have a good up-to-date guidebook for Rome, it should include the transportation details for getting to Sperlonga or Gaeta, and other beach destinations too.

Sorry for the bad info, guys. I thought that the bus stop labeled Nettuno, Via Nettuno, and Ristorante Nettuno were more indicative than they apparently are.