Is there bus transporation from Arlington, WA to Sequim, WA?

Chilena1 is correct, Greyhound would not work for such a trip. You would need to take a Community Transit bus from Arlington to Everett #200, 201,or 202 then an Everett Transit bus #23 to the Mulkiteo/Clinton Ferry and then another bus from Clinton to Keystone, another ferry to Port Townsend and a final bus to Sequim from the other side. Good Luck!