Your best chance for catching salmon will be way before you get to the San Juans. The west side of Whidbey Island will be chalked full of pinks. You will probably see them jumping at the surface if you are near land. Kill the engine and cast buzz bombs at them. In my experience with casting buzz bombs, pinks only hit as the BB is dropping, so definitely jig it in and be ready for light bites. If you decided to troll for pinks, you MUST troll slow. 2.5 knots, tops. Once in the Islands you will find more pinks on the west side of San Juan Island and they like to accumulate around Turn Point on Stuart Island.

There will be Chinook around. Without downriggers you will likely only catch them jigging. If you PM, I'll let you know where, let me know where you will be mooring.

I've personally never caught coho in the Islands but I know many are taken off the west side of San Juan Island. If you go this route, use a deep six, a flasher/dodger, and a coho killer w/scent. Target 3-3.5 knots and fish the tide rips.

Good luck and enjoy the scenery.