We have found wifi available at some resorts on the inside passage. As we have a trawler and carry our fuel, we don't stop at fuel docks, but I suspect that fuel docks would not have wifi as boats are not going to be allowed to linger, but need to move on to clear the dock.
The following info as of last summer.
Most resorts including those in the Broughtons have wifi, some included with the moorage, some for an extra charge. Greenway Sound includes wifi and garbage service with the moorage charge. Shearwater resort has pay-for wifi. I think Hartley Bay has free wifi.
Ketchikan does not have any wifi available at the harbor.
We use Sprint cell phones which work in most places with cell coverage. Sprint has an add on service for Canada that reduces the roaming charge from $0.40 to $0.20/min for voice. Sprint cell phones are not the best choice for Alaska. ATT and perhaps Verizon have much better coverage. This year I plan on buying a prepaid ATT phone for use in SE Alaska.
I use a Sprint broadband card for internet access and roaming in Canada is expensive at $2.00 per MB! I usually just check email (downloading headers only) and maybe the text-only weather forecasts.
Many areas on the Inside Passage do not have any cell phone or internet coverage, but do have good VHF coverage from the Coast Guard, both USA and Canadian.