Although only about 3% of the Island's population speak Jèrriais every day, there's reason for optimism: the census figure has indeed increased, particularly regarding children who speak it. There is government support for it and some signs in Jersey, as the one here, from Jersey Airport (from Wikipedia), are bilingual in English and Jèrriais. Jersey being a (British) Crown dependency, English is the main language on the island, having replaced French in the 19th century.
'Good morning/afternoon' is bouônjour and 'good evening' is bônsouair, whereas mèrcie is the word for 'thank you'. What distuingishes Jèrriais from other languages in the area is the voiced dental fricative (don't ask – just think of the 'th' in 'then'), as in extchûthez-mé, meaning 'excuse me', or bouôn annivèrsaithe, which means 'happy birthday'. You can hear these phrases at Les Pages Jèrriaises ('The Jèrriais Pages'), which have loads of information on the language.
(I'm off to bed, wishing you bouonne niet!)