Give the guys at Eureka Flyshop a call (707) 444-2000. They are very helpful and fish the area themselves quite often. They also have all the gear and flies you might need - they are one of those "local" fly shops that should be supported.
If I remember correctly, it is about anytime now that the lagoons breach and the fresh fish come in...
Let us know how you do, if you go. By the way, Stone Lagoon can be fished from shore fairly easily, nice walk along the beach, although if the sand bar is breached, you need to be careful - or take your surfboard
Have fun
CB
