Driving from Seattle to Telegraph from Seattle is a long trip and you might want to break it into a couple of days. I would highly recommend staying a day in Victoria. Victoria is a beautiful city and well worth a stop over. A visit to the Royal Victoria museum is a must and a great way to learn more about the first nations culture and natural history of British Columbia. From Victoria take the Trans Canada Hwy to highway 19 then follow signs to Port McNeil. Telegraph Cove is 10 minutes before Port Mcneil (about 6 hrs)
The shortest route to get to Telegraph Cove is to drive North to the Canadian border, once you cross the Canadian border it is just a short drive to Tsawassen ferry terminal. (you do not have to drive through Vancouver) Take the ferry from there to Duke Point in Nanaimo for the shortest route, or to Schwatz Bay if you want to visit Victoria. Going to Victoria will ad an extra couple of hours onto the trip. From Nanaimo take highway 19 following signs to Port McNeil. Telegraph Cove is 10 minutes before Port Mcneil. (about 4.5 hrs)
Web site: http://www.bcferries.com
Two other options include driving to Anacortes and taking the ferry through the San Juan Islands to Victoria on the Washington State Ferries. Or you can drive to Port Angeles on the Olympic Peninsula and take the ferry to Victoria on the Coho Ferry. There is also a passenger-only ferry running between Seattle and Victoria, the Victoria Clipper. From Victoria it is about a six hour drive to Port McNeill.
Washinton state ferries
Web site: http://www.wsdot.wa.gov/ferries/
Web site: www.cohoferry.com