There's only a bus and it's a long way, up to two hours depending on which bit of Lacanau you are heading for
The times for October will probably be the same as they are now but do check again nearer the time. Bus timetable, only available in French is at
The good news is that there is a flat fare of just €2,50 for single journeys on the Trans Gironde buses and a return fare of €4 available for up to six days coming back.
Thanks for that ink. I was hoping to head to the beach, seeing as it will be nearby.Edited: 3:51 am, February 15, 2013
(correction) "ink" should read link.
The beach at Lacanau will be deserted in October.