Cinque Terre

3 of the 5 villages were unaffected so they are fine Monterosso is planning to be ready by Easter Vernazza will more than likely still be under construction but parts of it will hopefully we open Yes you should prebook a hotel for May, it is a very popular destinations with a very limited number of rooms you should look at the RS Italy book for hotels and info about the villages to decide which village you would like to stay in and narrow down your hotel choices
also tripadvisor hotel reviews can be helpful

Chip, Based on the most recent information I've seen so far, I believe "the majority of the Cinque Terre" WILL BE in decent tourism shape by the beginning of May. Keep in mind that three of the five villages were not affected by the floods. It was mostly the "old town" section of Monterosso and Vernazza that were seriously impacted. Repairs in Monterosso have been progressing extremely well and as of this week a number of facilties have re-opened including a number of restaurants, Barber Shop, Butcher shop, Gelateria, etc. While they probably won't be completely back to the pre-flood status, I'm sure they will absolutely be ready to welcome tourists then, and will appreciate the support. The "new town" section (Fegina) was not affected as much, so it should be "business as usual" there. The situation in Vernazza is a bit more uncertain. I've heard that some lodgings are accepting bookings as of May 1st, so that's a hopeful sign, and a few businesses have re-opened there as well. Vernazza will not be back to pre-flood status by May 1st, but I'm sure it would worthwhile to stop there, as they would also very much appreciate the support from tourists. I would most definitely recommend pre-booking accommodations there! It's difficult to make suggestions without having some idea on your criteria, price range, or which of the five villages you want to stay in??? The Guidebook has lots of listings in different price ranges. I'd suggest having a look at Hotel Villa Steno in Monterosso. Happy travels!