Salisbury Beach faces NE and will pick up any swell from the north. Even a S wind blows offshore here, and the place breaks on all tides. The ideal conditions formula would be head-high NE swell, SW wind, and mid to high tide for some nice sucky, powerful wedges.
There is bound to be some drift in a north swell. Crowds are rare, even in summer, when 9-5pm surfing restrictions apply. There is camping in the Salisbury Beach State Reservation, just south of the main access road to the beach.