It sounds like you're planning on cruising over from the San Juans, so I'm not sure Port Renfrew is a great choice. The fishing is great in PR, but it means a long ride along the west coast, with few places to hide if the weather kicks up after you pass Sooke.
We've always fished the Sooke area out of Sunny Shores, but after basing a couple of trips in Becher Bay (Cheanuh) this year, we've decided we like it better - less distance to travel every morning to get to the hot spots, and it's right in the middle of the Sooke area, from Pedder Bay to Otter Point. Moorage at Cheanuh is an issue in the summer, though, so book early if that's when you plan on being there.
Best time of year - pretty much any time from June through to September.