Julie and Food Snob: Thank you both so very very much. I greatly appreciate your taking the time the spell out these things in such clear and helpful detail. (Btw, when people respond in the tone of the afore-mentioned, I simply pay no attention whatsoever to what's being said; just erase it from my mind.)
We'll be in the city for just 3 days, in mid-July (alas). Ah, if I could only be sure whether Capo or Westin had bette a/c. This is part of an 80th birthday celebration for my husband. That's one of the reasons that I'm trying so hard to find the right hotel for us.
Thanks again to all the good folks who have been so gracious with their help.

Air conditioning in Europe is nothing like air conditioning in the United States. BTU power is simply too expensive. If a trip depends on it, I would not go to Rome in July. In fact, I've never been to Rome in July or August. I prefer to be there when the Romans aren't on vacation and when there's less heat.

Air conditioning can also be a room-by-room problem. You never know. I know a celebrity who stays at the Waldorf Towers in NYC and the AC there can be hit or miss. The bigger the hotel, the easier to change rooms.

You might have better luck at a newer hotel like Hotel de Russie on Piazza del Popolo or Hotel Saint George on Via Giulia, one of my favorite areas in old Rome. Portrait Suites on the lovely Via Bocca di Leone near the Spanish Steps is getting good word of mouth. These are considered luxury choices and rooms can be pricey unless you can find a deal.