My wife and I are going to be visiting Rome next month and need advise on where to stay. We are flying into FCO. Our budget is around 150 euros a night. We are looking for the best area to stay that would be close to most of the main sites to see. Please help!

How many days are you planning for Rome?
There are many good choices of location to enjoy the old city. If you're a good walker you can enjoy a lot of Rome with a good plan and time. You can also quickly adapt to the buses if you study the routes before you arrive. A Roma pass might be a good value for you to save on a couple of major sights and unlimited bus transportation. (25 euro) find that here: http://www.romapass.it/acquista.aspx?t=acquisto
My preference is an apartment instead of a hotel if you're stay is three nights or longer. You should be able to find several in your budget price. Lots of folks can help you find a good apartment here on the site.

Sorry I forgot to mention we will be there for 4 nights. Just worried I may book the hotel in the wrong city or bad part of town.

Go to http://www.venere.com/italy/rome/ and enter your dates and budget and see what comes up. The most central areas are Pantheon, Navona and Trevi. Lower-cost areas are Esquilino, Marsala, Colosseum, Repubblica and Prati. Avoid all other areas, because they are too expensive, too far or not well connected by transport. All of central Rome is safe; the areas near Termini (Esquilino, Marsala, Repubblica) are charmless, but they are not unsafe.

Easy to do in March with with your budget.
There are lots of reviews and suggestions for suitable hotels
on this forum,
I would recommend
Residenza Canali Coronari
http://www.residenzacanali.com/?lang=en

Close to Piazza Navona and within walking distance of many sites and restaurants.