Hi,
I'm not in Rome but about 20km south, near Frascati. Although I go into Rome often I can't really advise on places to live. But there are a couple of websites that may be helpful (if you haven't looked at them already)
www.romemama.com/ and rome.angloinfo.com/ Both have forums discussing areas to live. They also have messages from Mums in central Rome looking for playdates etc.
I would think it would be fairly easy to find other English speakers (if that is what you want) for friends and for yourself and your son. There is a fairly large expat community in Rome and a few English playgroups. It is not something I am involved in at all but they are there. You will probably also find other Mums in your situation through your husband's work who would be happy to meet up.
I have also found Italian people, even when you speak hardly any Italian to be welcoming, and if you have neighbours, for example, with young children they would probably be very open to you popping in for a coffee while the children play for a bit, and very open to invites for the same from you.
Where we live is great. We have two English speaking nursery schools here, an international school for older kids, rented housing is fairly reasonable (although it can take a bit of time to find something), it is a small town with very friendly people (both Italians and expats) and for us it is nice to be out of the city with a house and garden. However, it may be too inconvenient for your husband for work, and you may prefer to live in the city in any case.
Hope this is useful
Alison