Even out of season,  #15 Connex Bus is a reliable clean servce (every 30 mins or so),  takes about 25mins to the new modern bus terminal ans costs just £1.60/person.  With taxi fares around £12-15 it is well-priced.  Try and get in queue early and get luggage space at front with a seat nearby.  Runs also on Sundays - most connex services do not..Back to airport is from the new terminal.

In fact,  the Connex buses offer plenty of key  over the island routes at £1.60/leg.  Their web site is mybus.je