I was there in January.. Great spot with a loooooong (5km) wide beach...
Wind usually from nortehrnly directions which means flat to small chops close to harbour/town and great waves further south.
During summer the trade winds pick up during the morning and increases until 3 - 4 p.m.. Be sure to bring small kites
.. I spoke to a few of the locals and lately the wind has been more random and it looks like the windy city of Africa will become a has been unfortuntaly...
If you happen to have alot of old equipment or gear you would like to get rid of bring it along as the locals down there are in really bad shape gearwise....especially the small stuf like hp leashes, extra lines and so on.
Be sure also to visit Sidi kaoki, 20 minutes drive south of from Essaouria. Great beach, with a small surf centre, beachbreak, more wind and very few people.
Have fun!!!