Hiking in Cinque Terre

Updating web sites is not always top priority in Italy. I'd consider this one first: http://www.parconazionale5terre.it/sentieri-outdoor.php, which still shows all coastal routes closed between the five towns, as they have been since last November's round of storms. Before that, only Monterosso-Vernazza-Corniglia were open in the past few years. Check closer to your travel date and re-confirm locally.

Just backing up Laura here: The website she's given you is your best resource for which trails are or are not open at any given time. In case you haven't figured it out, here it is in English:

http://www.parconazionale5terre.it/Eindex.php

Trail map and closures:
http://www.parconazionale5terre.it/Esentieri-outdoor.php

As far as "each website", be cautious what is coming up in a google search as there's a lot of outdated info out there. That isn't necessarily the fault of those sites as much as the landscape of the C.T. is fragile so trails which may be open one day can close to weather or unexpected damage the next. So, what you might be able to trek in May is dependent on conditions when you're there.

It's almost certain that the Sentiero Azzurro (Blue Path/SVA2) between Corniglia and Manarola and between Manarola and Riomaggiore will be closed, although there's some question about Corniglia >Manarola. To get around them, you'd have to reference the map for higher/longer trails which may be open.

Trails can close on short notice. So it's probably pointless to plan too much in advance. Plan to hike south from Monterosso to Vernazza and then Vernazza to Corniglia. I think the main trails south of there to Riomaggiore are still closed, though there are some "detour" trails that take longer (haven't hiked them). If a trail you had expected to hike is closed when you get there, then find another hike. There are some alternate hikes e.g. from Levanto down to Monterosso. You don't really have very much time, anyway.

nancy,

As the others have mentioned, wait until closer to your visit to check the status of the trails. Check with the staff at your hotel when you arrive, as they will have the most current information.

If you're concerned only with the popular Sentiero Azzurro trails, it's likely that the Monterosso - Vernazza - Corniglia sections will be open at that time of year, and the Corniglia - Manarola - Riomaggiore sections will remain closed. Note that you'll need a Park Pass to hike those trails. The passes are easily obtainable once you arrive there.

Trails can literally close overnight. If there is poor weather/heavy rain expect that trails that have been open will close. You will literally find out when you get to the trail heads if they have been closed. So...if the weather turns foul while you are there it's good to have a backup plan.