Yes, GALLEY is a Scrabble word!

Letter values in Scrabble US: G 2, A 1, L 1, L 1, E 1, Y 4.

Is it a valid word?

GALLEY is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a large medieval vessel with a single deck propelled by sails and oars with guns at stern and prow; a complement of 1,000 men; used mainly in the Mediterranean for war and trading
(classical antiquity) a crescent-shaped seagoing vessel propelled by oars
the kitchen area for food preparation on an airliner
the area for food preparation on a ship

Also: ship's galley.