It leaves from the city every 30 mins on the hour and half hour so wherever you are add 5-20 mins.
It stops at many pubs in San Lazaro
It also stops just near the albergue in lavacolla.
Do yourself a favour. It can be busy on the bus with 80 standing.
Get out early and have a calm drink 10 minutes from the airport and wave the pilgrims in.
Also take a wee drink to the airport and some arzua or tetilla cheese.
Enjoy a calm cost efficient end to the camino