Stone horse is on route 28 so just take a left from the driveway and keep going. It comes to a "T" at Shore Rd, take a right. Go 100-200 yards and the mecca will open before your eyes. You can park there between 4pm and 9am every day and it's a great spot for warming up as well as hooking up.
If you feel adventurous, walk to the right and keep the fly low and deep on the sand. If there is any current you should find them. Otherwise walk over the sand to the inside basin called the "tub" and there should be fish there too especially at low tide in the deep bucket at the top end.
Or go back on Shore road to the north and try the accesses to Pleasant Bay (check mapquest etc). I suggest Minister's point, the Cowyard for starters.
But you don't have to go that far - along Rte 28 closer to the Stone Horse there are many accesses to the Nantucket Sound shoreline which is always good in spring and fall. Head back toward the mainland a bit and look for Red River, Herring River, Bass River and try your luck around the high tides or start of the outgoing at the river mouths.
As the date approaches we should post estimated arrival times if you are looking for someone to point you in the right direction.
IFFF Certified THCI @ 2005
Capeflyfisher Guide Service
Island Hopper, Guitarist, Incurable Dreamer
and Founder, Worldwide Flyfishing Forum