Best months are May until October; the dry season. For the walk; best time at low tide to walk around ahuge rock.
Sakalava is a gorgeous beach which can be combined with a walk via Pigeon Bay to Dune Bay and back. The other option is a taxi to Sakalava and a walk until the village Ramena. The walk takes about three hours to unspoilt and empty beaches and bays. The Sakalava Bay is accessible by car on a sandy road. The beach is well known for kitesurfing. There are a few accommodations along the beach. If you visit Ankarana and Amber Mountain you should plan an additional day for it.