You've received lots of good advice. Just two things: Please please please stay IN Rome. I think you'll be much happier if you do, for the reasons noted above. And with only 4.5 days in Rome, you really don't have time for a daytrip to Pompeii. That much time in Rome will barely scratch the surface.

We did Paris, Rome, and Florence last summer as our first European adventure-and we're 50+. I took many weekday evenings (after teaching all day) and booked everything on line, using TripAdvisor for many reviews. Fodor's guides are great.Invest in the one for Rome b/c he gives many websites for museums, etc.,and you can plan your trip down to where to get the next latte. We used Rick Steve's, too, but I find he speaks to the younger crowd. We stayed at The Raphael in Rome and LOVED it. (www.raphaelhotel.com) Elegant, but not too over-the-top expensive. After a day's art and museums, just turn the corner from your hotel and walk the cobbled streets to a nearby outdoor cafe for pasta and chianti. And stash the jeans, tennis shoes,and baseball hats-at least for dinner. (You can always tell who the American tourists are). You will also discover that Europeans eat HALF the portions that we do. At first I was hungry; then I got used to it! Take the train to Florence (Firenze). You can book it online through Trentalia and even have the tickets mailed to you stateside. A great hotel in Florence is Hotel Degli Orafi. We lucked out with a room with a balcony looking over the river. Try booking with the hotels' websites and tell them this is your first trip to Rome, etc. Sometimes you get an upgrade, which is so nice of them. We enjoyed Firenze more than Rome...more relaxed, toured the boyhood home of Michaelangelo. Amazing. You will have so much fun!

We've stayed at Hotel Riva and found that the rooms are an excellent value. Some rooms are nicer than others. Make sure yours has air conditioning as it will be nicer. I believe rooms 27 or 26 have air and are nice.
You might want to consider staying in Trastevere when in Rome. We stayed at Arco del Lauro. Check it out on Trip Advisor. It couldn't have been nicer.It is in a quiet area but only minutes from restaurants, shops and only a 10-15 minute walk to campo di fiore. I highly recommend it.

We have just returned from a 10 day trip around Italy which included 5 nights in Rome, 3 in Florence and 2 in Venice and this did not allow time for any day trips as there is so much to see in each of the cities.
We travelled between the cities by train and, in most cases, bought the train tickets the day before we were due to travel and had no trouble getting seats. You will be there at a busier time though, so it may be necessary to purchase your tickets a few days ahead of time. The tickets can be bought at the stations using very easy to use self-service machines which have an English option. For more information on train travel you can try these websites:
http://www.trenitalia.com/en/index2.html and
http://www.slowtrav.com/italy/trains/index.htm
As far as accommodation is concerned, we stayed in an apartment in Rome (http://www.romanholiday.it/roma_colo...s_aurea_uk.htm) and found it to be inexpensive, very comfortable and conveniently situated (very close to the Colosseum).
In Florence we stayed in an hotel within walking distance of the station (and everything else) called Hotel Montreal and, although a budget hotel, found it clean and comfortable (http://www.hotelmontreal.com/index.php).
In Venice we also stayed in a very clean and comfortable hotel called Hotel Palazzo Guardi (http://www.palazzoguardivenice.com/en/index.htm).
Although we were there out of season, all of the accommodation was around E100 per room per night (for four of us, including 2 teenage children) and all also had air conditioning.

Another option for getting to Pompeii from Rome is the shuttle bus operated by Enjoy Rome at www.enjoyrome.com. Unlike the more expensive tours that operate from Rome, this provides transportation only, and does not stop at souvenir shops or restaurants. It costs 55 euros per person and does not include admission to the ruins. You have time from 11 AM to 3:30 PM to visit the ruins, and you are back in Rome in time for dinner.

I have taken the shuttle bus and the train on day trips from Rome to Pompeii. The shuttle bus was more relaxing, although the train was not difficult at all.

The day trips to Pompeii were absolute highlights of both my visits to Rome.

Plans are coming along nicely. I'd add a day to Venice, subtracting it from Florence.

And be sure all hotels are in the *central* area of each city so you can walk to many of the things you'll want to see.

M,

I would also agree that the time you have planned for Rome doesn't allow for a day trip to Pompeii. You will return - save Pompeii for a southern Italy trip - thre is much to see and do!

You might try the Hotel Giardino Rome - very reasonable and a great location. I stayed there in Sept 05 in a single with bath and breakfast for 90E/nt.

Buon viaggio!

Thank you everyone for your assistance. I think we need to regroup and look at hotels within Rome proper.

I will come back with another refined itinerary and more questions I'm sure!

My advice on the whole
Florence
Siena
Lucca
Pisa priority is as I've listed it. The main reason to visit Pisa is the Tower and the surrounding religious buildings. Lucca has great religious buildings, 1550 city walls and great towers. Siena is smaller than Florence (and was defeated by Florence) but has wonderful buildings and is a hill top city. Florence has the best biggest buildings.

All will be bustling with Lucca the most open

Another vote for eliminating the day trip to Pompeii if you only have 4.5 days in Rome. You could stay flexible about the possibility of a much shorter day trip to Ostia Antica but with the time you have I think you would do better to concentrate on the Forum, Palatine, Pantheon, Catacombs/Appian Way/aqueducts plus the many other Roman ruins in the city.

I also recommend trying to stay in the central historic district in Rome rather than outside the city. You might be able to find an apartment if you are staying 5 nights (I am still a little confused about your no of nights in each location vs no of days for sightseeing). The apartments tend to be better value for the money in terms of space especially if you can find a 2 BR one that works well for two couples.

MaryRay

I'm so glad you are looking for a place to stay within Rome. Although for many the medieval center is favorite area, and include me in that, if I were on your budget I would consider staying in the Vatican area, or north of Termini (there are some recommended streets, but I'm sorry I don't know their names) or nearer the Forum/Coleseum.

I've seen budget hotels recommended in those areas.

Also, check the B&B recs on tripadvisor.com. I've found some good things there.

Eariler, mimar mentioned buying train tickets at travel agencies in Italy. I like to do that, too. Going to a train station just to buy tickets is often inconvenient. Any agency that features the Trenitalia logo will sell you tickets.