Cinque Terra

Great idea! IMHO, the CT are at their best in June or September. July-August is too hot and crowded. As for recommendations for lodging, do you have the RS Italy book? It's the perfect starting point for all your questions. As for length of time, 3 nights in the CT would be plenty, especially considering how much more there is to see in Italy. Because the flights to/from Italy will be such a huge percentage of your budget, I suggest staying as long as possible in Italy. If you've never been before, the classic first visit to Italy includes Rome, Florence and Venice. Have a great time.

Rick's book Italy has detail on the CT. It's a favorite destination of his, so his book has good coverage of CT, compared to some other books out there. May or Sept are, generally, good months (but with weather, you never know): you avoid the summer but have a reasonable chance of nice weather.

Weather is a crap shoot. We were there this last September for 3 nights. The day we arrived was beautiful. The rest of the time it was raining or overcast. It was interesting to watch them pull all the boats in when the storm was approaching. As far as when to book - that depends. Do you like knowing ahead of time where you will be staying, or are you more of a fly-by-the-seat-of-your-pants kind of person? I tried booking a place in January for our September trip, and the place was already booked. Have either of you been to Italy before? If not, IMO 3 nights in CT is plenty. I would stay in Italy as long as possible and see some other areas. I used the Rick Steves Italy book to plan our trip.

Rick is the king of the CT. His blue travel guidebooks can be seen everywhere.
Having stayed there a few times, I would recommend Riomaggiore or Manarola over Vernazza. Vernazza is beautiful but over-run with daytrippers during the summer. Best to join the others and daytrip there, staying elswhere (be sure to stop at Il Pirata for the cannoli!!!) Plus in Riomaggiore & Manarola you can usually find a room with a terrace (not many in Vernazza). The CT is a great base for also visiting the Ligurian cities of Santa Margherita, Levanto, Portofino and others. Lots of things to do in the CT, and a great place to relax. We've stayed with Rick's recommended Edi's Rooms. Call them, they aren't very prompt responding to emails.

We went to Cinque Terre in May 2009 and the weather was perfect. It was still warm but in the evenings it was cooler which was nice. I always travel with a Rick Steve's book. He has the best recommendations that I have found. My husband and I stayed at Edi's Rooms in Riomaggiore (www.wel.it/Vesignaedi). This was our favorite place we stayed in Italy. We were in the Case Mimi room which had a huge balcony overlooking the sea. It was very clean and just the perfect location. It also had a refrigerator, coffee maker, and table and chairs inside the room to eat. This room was 80EUR (not sure if the price has changed since). They did have other rooms to rent for less as well. Edi is also recommended in the Rick Steve's books .
We liked staying in Riomaggiore because it was connected to the Via Dell Amore which is an easy path to the next town Manarola (approx 20min walk). It's also great to watch the sunset from the rocks in Riomaggiore. It's not as crowded as Vernazza which is why we liked it here. I do recommend like the other post to stop at Il Pirate in Vernazza for a cannoli! It was one of the best things I ate! Have a great trip!

We were there in Sept last year (while on a cruise) only as a daytrip. Great weather! Rio Maggiore and Vernazza are the best. After lunch and small shopping in Vernazza we took a walk in the back of the shops and it's amazing to see how people there continue to maintain a living in difficult circumstances (I meant living on steep mpountainous terrain - their pigs, goats, chickens and geese were in very narrow pens, but all seemed healthy and happy.)