Thats a tough call. There is so much to see in the area besides just downtown that I think a car for one or two days would be a great idea..especially if the weather is nice. A drive out to Snoqualmie Falls, the woodinville wineries, Ballard locks are all worthy side trips.

There is good bus service from the airport and Bellevue, where you'll find less expensive hotels and sometimes free parking if you do decide on a car.