hjones,
As the others have mentioned, you shouldn't have too many language difficulties in Italy. Many of those in tourist-related businesses (hotels, restaurants, etc.) will have at least some ability to speak English. That applies to others in Italy as well. A few years ago, I asked a police officer in Florence for directions to a hotel in Italian, and he provided the directions in perfect English.
However, it's polite to learn some of the usual greetings, etc. such as "good morning, good evening, please, thank you", etc. In my experience, Italians really seem to appreciate visitors making an effort with the language. As you already have a foundation in Spanish that should be relatively easy, since both languages are from the same "family" and are similar in many ways. I agree with the others that it would be a good idea to pick up a copy of the Italian Phrase Book as it will be good reference during your trip (and good reading on the flight over).
One point to mention though. I found it almost impossible to study Italian and Spanish at the same time, as many of the words are similar, so I'd get confused and would go into "brain lock". You may find that too. In any case, Europeans are very clever with languages, and you may find that some of the people you're dealing with in Italy can also speak Spanish.
One final point - if this is your first trip to Europe, I'd also suggest reading Europe Through The Back Door prior to your trip, as it provides a lot of good information on the "differences" you'll encounter. A few examples - numbers will be written differently and the floor numbers of buildings are specified differently. Have a look at THIS short tutorial for details.