I wondering if anyone knows if it's possible to take a ferry or boat from Nice area to Cinque Terre in May.
I don't think that you can do this on one ferry or even one ferry system. What can be done is to take the ferry from Nice to Bastia, Corsica and then change ferries to go from Bastia to Genoa. You then most likely will then need to take the train to Santa Margherita-Ligure Portofino and pick up the Golfo Paradiso ferry from Portofino to the CT. Definitely not fast or easy.
jennkeen,
AFAIK, there are no Ferries from Nice to the Cinque Terre. I'm assuming you weren't planning to just make a day trip there, but will be staying in the C.T.
The easiest and quickest travel route is via train, and even so the trip will be 5-6 hours. There's always one change at Ventimiglia and perhaps another at Genova (or other locations in Italy).
Happy travels!