Drive north to Anacortes and take the bridge at Deception Pass. It takes about two hours to drive to Oak Harbor, which is on the north end of the island or three hours to Langley on the south end of the island.

The ferry saves a lot of time if your destination is at the south end of the island.

There should be no reason to worry about the ferry service in late September.

HTTY

Thanks, what part of the island would be preferable to visit, the north end or the south?
Also, do most people take their vehicle on the ferry?

My favorite places on Whidbey Island are in the north end: Deception Pass, Penn Cove (source of our famous mussels), and Coupeville.

If you like historic towns, you could drive up I-5 to Conway, through the Skagit Valley to La Conner and from there to Deception Pass, Penn Cove, and Coupeville. From there you could take the ferry to Port Townsend and return to Seattle via Port Gamble and the ferry that sails between Kingston to Edmonds.

Why are you interested in Whidbey Island rather than some other destination near Seattle, such as Mt. Rainier, the San Juan Islands, the Olympic Peninsula?

HTTY

PS I don't know the proportion of drivers who use the ferry vs. those who drive onto the island over the Deception Pass Bridge.

It's an ideal day loop trip. Head north to the Mukilteo ferry (use SR 526, the "Boeing Freeway" that passes the Boeing widebody plant - biggest building in the world.) Then stop at (IMO) the cutest town on Whidbey, Langley (the turnoff is only a couple of miles from the ferry dock.) Then up the island, possibly stopping at Greenbank Farm for a bite (or at least, a piece of pie - OMG) then to Coupeville, then through Oak Harbor to Deception Pass. Over the bridge thence east on SR 20 toward the freeway, but do the La Conner detour as HTTY suggests (but my route is in reverse.)

Then back to I-5 and badda bing, an hour back to town. GREAT day trip. In late September you might even have some fall color on the island.

Thanks again. I picked Whidbey because I thought it would be easier to get there on the weekend. I heard that the ferry lines can be long to San Juan Islands. Maybe this would not be true for weekend of Sept 22nd? I do not want to book ahead, since weather may be iffy.

I do plan on a day trip to Mount Rainier as well. Any ideas of a good moderate hiking trail there?
Should I head to Paradise?

The Mukilteo-Whidbey ferry is nothing like the San Juan Islands ferry - much shorter, much more frequent, no reservations needed (nor accepted.) In late September I'd be surprised if you have to wait more than 20 min. for the ferry, depending on when you get into the lineup. Plus it's a much shorter drive from Seattle (25 min. vs. nearly 2 hours for Anacortes.)

Probably Paradise is your best bet - you will need to watch the weather at altitude before picking a hike. http://www.nps.gov/mora/planyourvisit/paradise.htm/index.htm

Should I head to Paradise?

Yes, and the drive between Paradise and Box Canyon is one of my favorites for views of the Cascades. Take the one-way road out of the Paradise parking lot.

HTTY

PS Go to Mt Rainier on a clear day rather than on a day when the mountain is shrouded by clouds.

I love the loop trip described above - in either direction, though your choice might depend on what meal you want to enjoy in Langley, but be sure to stop for pie at Greenbank. Langley and La Connor are both adorable. We also saw lots of bald eagles while driving Whidbey Island. A great day trip. Ferry shouldn't be a problem, but deception pass is worth the drive north.