This is a report of my first successful attempt at taking transit to go hiking:
Rhododendron State Park, on Whidbey Island, is no longer a state park, but that's what you'll want to enter as your destination if using the Island Transit Trip Planner, at .
The Island Transit Route 1 weekday bus departs from the Clinton ferry terminal at :15 past every hour, so I planned backwards from there to minimize layover times. See , and for complete schedule information, and to plan your trip from the Seattle metro area.
The only warning that you're getting close is a small, brown sign that says "Park Ahead," so I recommend letting the driver know where you're headed. Once inside the park entrance, the profusion of rhododendrons begins. They're not in bloom yet, and probably won't be for another two weeks.
I walked the length of Rhodie Road, a gated paved road padded with organic material, and came back via Grandpa's Legacy trail. Spent a lot of time wondering what Grandpa's legacy could be. This portion of the walk was on real trail through mature mixed forest peppered with rhododendrons. There's more opportunities for wandering, but the bus only comes by once an hour, and I wanted to check out South Whidbey State Park before the rain arrived.
When you get back to the highway, turn right (east), and walk about 1/4 mile to the bus stop. I didn't know where the stop was, and the driver did stop for me, but warned me that it's not a safe place for them to pull over.
South Whidbey has quite a few more trail miles, through forest atop a bluff overlooking the beach to the Olympic peninsula, and trails on the north side of the highway that wander past skunk cabbage and coralroot, with an ancient cedar tree as a star attraction.