Yes, you have to cross the border and yes you have to pay to park but DO GO! There is a myriad of trails throughout this Fidalgo - Whidbey Islands park to explore, fantastic scenery, wildflowers and wildlife. We left Maple Ridge at 8am, took the truckers'crossing in Surrey, whipped down the I-5 and 2 hours later were in the park. I would suggest downloading a park map for orientation. We parked in the Bowman Bay lot, a good starting point. There is a Discovery Pass pay station there -cost is $10 american and it takes cash or credit cards.
We hiked the Lottie Point loop first with its old firs and peeling bark madrone trees. There are some steep high narrow sections and a fallen tree to maneuver over (hang onto your kids) but the trail is well maintained and leads to fine water views. Crowds were nonexistent. We then took the Lighthouse Point trail with stunning views of the bridge, little coves, kayakers, wildflowers, ducks, seals, a snake, even a killdeer sitting on her nest on the marshy beach section. We went up and around the point, eventually veering off the main trail to a less traveled one. This soon split into upper and lower trails. The lower one led us to a sketchy steep section and what appeared to be a sheer drop off near the water. Our dog was not happy. We backtracked to the upper trail, taking us through some overgrown salal and then back onto the main trail. Time for lunch at Bowman Bay beach!
Another popular hike nearby is the one to Rosario Head. While munching on our sandwiches we kept an eye out and noticed that quite a crowd was building up over there. We decided to save it for another day and headed over the Deception Pass bridge to the Whidbey Island side of the park. Now, that bridge is worth the drive itself. Built in 1935 it's actually 2 bridges in one; it spans Deception Pass almost 200 feet below, and is structurally a fine work of art. You'll want to stop and look it over.
We parked in the vista lot just past the bridge. After gawking at the underbelly of the bridge we set out on the summit trail and, after a bit of a grunty steep section, in no time we were on the top of Goose Rock. The wildflowers are lovely here. This area is known as the Balds - 11,000 years ago a receding ice sheet scoured the hilltop down to bare rock. It has taken many 1000's of years for the soil and plant life to build up and we are advised to tread lightly, to stay off the vegetation.
We then drove along Cranberry Lake, sighting a grebe on the way, and ended up on West Beach, a perfect spot to finish the day.
FYI: If you plan to visit a few of Washington's state parks you may want to consider
purchasing an annual Discover Pass for $30. Same thing if you plan to explore Mt Baker-Snoqualmie National Forest with its many beautiful hikes - an annual Northwest Forest Pass is available for $30 (otherwise it's $5 for a day pass).