st annes - park at the car park where the sand yachts used to go from. DOn't need to worry about tides cos always plenty of beach. Make sure you lock up at this time of year thoug...
I ride a bit further down from the St Annes beach (that ones always quite busy) at Preesall/Knott End - its great, dead flat and you rarely see another person/dog/anything on there.