Commuting Seattle-Olympia

Hi, I am planning to spend 3 months in Olympia (North East side of town). However, since it is a small town I am considering to better stay in Seattle and commute at least 4 days a week. There it seems to be a bus that takes quite long and by car it would be at least an hour. I would very much appreciate if someone could tell me whether traffic gets usually heavy in Seattle or not. Also, I would appreciate if someone could tell me where is the main bus station in town in case I end up commuting by bus. Thanks a lot in advance for any help!