I have been unsuccessful in finding an economical room in Monterosso for late May. Rick Steve's suggest private rooms, but I'm not sure how to go about finding these before I arrive. Any suggestions?
For many of these "private" rooms, you can't find them in advance. They don't have websites or email addresses. You just show up and try to get lucky. There are room reps at the train stations that solicit rooms as you get off the train. Also, there is at least one store front room agency that I saw in Monterosso where you walk in, stand in line and see what's available. Finally, ask the merchants. They all seem to have a relative or friend with a nice room to rent. It's really big business in the summer months and it's great extra income.
I wouldn't be prepared to be that adventureous but many people on this site have posted that they have used this strategy and have found great rooms.
Once summer arrives in the CT, I'm not sure that anything there is "economical" especially with current exchange rate for Euros.
Try Manuel's Guesthouse. This is mentioned in Rick's book and we know people who just loved it. It is only 60 euros a night for a couple. It is online at www.manuelsguesthouse.com They do not take credit card ahead of time but will reserve you a room/apartment.