I'm wondering about how phone service is in Vancouver (and the rest of the cruise, also...)
We were in the Vancouver area for one night before the cruise and didn't do any significant activities. So we avoided signing up for an international plan for that brief time. We looked into it a bit. But the cost just didn't make sense for our needs. I did use an AT&T/iPhone for GPS maps to get to the hotel and then to the port. I turned off data roaming, so the Google maps app I used just relied on the cached data downloaded in the USA before driving to the hotel or in the hotel before going to the port terminal. I couldn't keep the phone in airplane mode, or the GPS wouldn't work. The phone connected to the Rogers network while we were in Canada. But I didn't make any phone calls or text. Hopefully others have more information about international plans or SIM cards local to Canada if you need that. I suspect that if you want to go the route of swapping SIMs, you need to make sure your device is carrier unlocked by AT&T prior to traveling.
As for Alaska, I didn't have any trouble connecting to AT&T in the three ports. I actually forgot to turn on cellular data in Skagway, so I don't know for sure how it would have performed there. But the data worked great in Juneau and Ketchikan, even from the ship in port.
I actually didn't try to connect to the AT&T network while at sea. We were always so busy with the many awesome activities onboard. And honestly, it was so nice to just get off the grid for a while. We did sign up for the free 50 MB of Connect @Sea WiFi data. We had two staterooms, so we had a total of 100 MB we could use. But we used it so rarely that we didn't even come close to using up that much data. Again, we were plenty occupied with activities on the ship that spending time online was one of the last things we were interested in doing. The Connect @Sea connection was a little bit confusing to use at first. I just needed to figure out the difference between using the WiFi for Internet access versus for Navigator app access. But once we got the hang of it, it did work quite well, and was only a bit sluggish for our uses. We used it on an iPhone and an iPad.
We did make extensive use of the onboard WiFi to connect to the
Disney Cruise Line Navigator app. That worked very well for us. It was great to be able to see maps of the ship, dinner menus, and activity schedules. We used it to make sure we didn't miss any of our favorite character meet-and-greets and to keep our children updated on the current club/lab/Edge activities.
After the cruise, we drove straight from the port to the USA. I had cached map data on my phone from the shipboard WiFi prior to disembarkation. So, once again, we didn't really need international phone service at that time.