We love Rome, and have had several short breaks there. stay as central as you can, we take taxis which are cheap, and the hotel will call one for you and say where you want to go( not many Italians speak English). or you can walk back( after taking a taxi to wherever you want to go.) it's a marvellous city, just enjoy strolling around, people watching, and stop for a coffee, remember to take a map wherever you go. it always feels safe ( to us) even at night time. the Vatican Museum is a must, however long it takes to queue,
Also the colisseum, and the forum, where you can just wander around at your own leisure. St. Peters of course, and nearly all churches are worth a look.The Trevi Fountain ( 3 coins in the fountain, film) and the Spanish Steps.Lots of nice and resonably priced places to eat. take a small Italian phrase book with you, in case you get stuck and need something.Lastly, have a great time and take lots of photos!