I'm in agreement with Sheldon, both on timing and locations. Summer is a fun time to visit the Oregon coast for the average tourist, but that marine fog layer sits just off the coast much of the time and usually kills the sunsets.
May is a great time to visit - more chance of good weather than early Spring, but the fog layer hasn't settled in for the summer. Look for very low tide days for great tidepooling.
Bandon is, IMO, the prime spot on the coast for photographers - the sea stacks make wonderful subjects in almost any weather and time of day, and especially at sunset. If you base yourself there, you can also work north to the Sunset Bay - Cape Arago - Shore Acres State Parks complex, and south to Cape Blanco State Park for lighthouses, waves crashing on rugged cliffs, wildflowers and formal gardens at Shore Acres. More great sea stacks further south from Cape Sebastian to Harris Beach just above the California border.
There are also several beautiful waterfalls in the Coast Range mountains, and in late May the rhododendrons will be blooming in the forests.