Ahhh... Whidbey Island, WA, reporting in here.
Driving from Canada, down the I-5, look for signs pointing to Anacortes (if you want to see the San Juan Islands) and Whidbey Island (Hwy 20, South). Go to Whidbey Island. Stop at the DECEPTION PASS BRIDGE for breathtaking views West (toward the San Juans) and East (toward "America" - that's what we islanders call the mainland. And we sometimes call it "the Dark Side" as well. )
A mile or so south of DECEPTION PASS BRIDGE is DECEPTION PASS STATE PARK. Lovely place to camp. Great birding area. You might even see orca whales. Nice hiking trails, and fishing along the pebble beaches.
http://www.parks.wa.gov/parkpage.asp?selec...eception%20Pass
Continue south on Hwy 20, to KEYSTONE/PT TOWNSEND FERRY. There a campsite called FT CASEY STATE PARK has a small camping area right on the pebble beach overlooking the comings and goings of the ferry. It's a bit windy there, but lovely and fun. Great walking beach where we've found small agates. Wave to folks on the ferries. Wonderful site. Even though we only live 20 miles south of there, we sometimes go camping there just for the fun of it!
http://www.parks.wa.gov/parkpage.asp?selec...rk=Fort%20Casey
YOu will want to make a reservation to cross on the KEYSTONE/PORT TOWNSEND FERRY. Check the WA state ferry website. You don't have to have a reservation, but it helps.
http://www.wsdot.wa.gov/ferries/
So you have two options there:
1. Cross on the KEYSTONE FERRY to the OLYMPIC PENNINSULA. Campsites along the Pacific-facing West Coast (Hwy 101) are wonderful. There are campgrounds at Kalaloch and Pacific Beach. I love Kalaloch. If you have dogs who like to run themselves silly along miles of beach, this is the place to be. Campsite are under wooded shelter about 30-50 ft above sea level, then trails down to driftwood beaches. Great sunsets. I truly love this area.
http://www.trails.com/tcatalog_trail...id=HGW206-001A
2. BUT, if you don't want to go to the Olympic Penninsula, from the Keystone Ferry go back to Hwy 20 south - it turns into Hwy 525 to the CLINTON/MUKILTEO FERRY and back to the I-5 south. But before you leave Whidbey Island, there's SOUTH WHIDBEY STATE PARK on the west-facing side in a fir forest. Very nice, but the steps to the beach were trashed in a storm 2 years ago and have not yet been replaced. Still, there are nice hiking trails in and around the park.
http://www.parks.wa.gov/parkpage.asp?selec...South%20Whidbey
And be sure to visit LANGLEY, WA - that's where we live

- a thoroughly charming small seaside village about 4 miles off Hwy 525, to the northeast, facing Mt Baker - art & antique shops, nice restaurants, friendly folk... very picturesque.
http://www.visitlangley.com/
If you take the Clinton/Mukilteo ferry and rejoin the I-5 south, that will take you through Seattle, Tacoma and Olympia.
Happy cramping!
Sharen Heath