My son is traveling to Rome unexpectedly following a business trip. He will be there for a 4 night stay the end of March. I have recommended Hotel Ponte Sisto where we are staying in May but it is not available. Can anyone recommend a 3 or 4 star hotel in the Campio di Fiori/Piazza Novona/Trastevere area. He is in this 30's and single so will be looking for a lively area with some nightlife.

hello - the hotel navona, located in the piazza navona, is in the area where there's lots of great bars and good restaurants. its not 3 or 4 stars, but its a really great place to stay.
via dei sediari, 8.
www.hotelnavona.com

I like Hotel Marcus, near the plaza. It has a 2** rating. But in my mind it’s a 3* interior, and location is great.

http://www.abaka.com/Italy/Marcus/

I also once stayed and like Hotel Teatro Di Pompeo on Campo Fiori.

http://www.romeguide.it/teatrodipompeo/hotel.html

I loved this hotel, it’s kind of majik. You can drink some wine at night, walk out and wonder through the little streets at night, staring at walls of various buildings…… and then come back not to a “hotel”, but one of such buildings….

Have him check these sites which specialize in late bookings:
http://www.laterooms.com
http://www.ratestogo.com

I liked Hotel Portoghesi which is just off the Piazza Navona near the river.

My "go-to" three star near the Campo de' Fiori is the Teatro di Pompeo....comfortable, convenient, friendly staff. About Euro 190 for double.....Euro 150 for a single.

http://www.romeby.com/teatropompeo

Jim:
When you go to the Hotel Teatro di Pompeo website (in the photo gallery) they have things listed on there as "Dependance Rooms." What is that?

Here is the page I see them on:
http://www.romeby.com/teatropompeo/pages/gallery.htm

Thanks.

A "dependance room"--dipendenza in Italian--is just an annex to the hotel. In this case, the hotel has rooms in the building across the piazza and uses it when the hotel is filled up. Other than the fact that there is no elevator, it is the same as staying at the hotel proper.