You will not be able to watch the regional broadcasts if you are outside the Flames region (which is all of Alberta, Saskatchewan, the Northwest Territories, and Nunavut). In order to view the regional broadcasts, you would need to subscribe to the Sportsnet Now Premium tier:
https://secure.snnow.ca/pricing -- which is $35 for a month. Also, if you have access to an Alberta-based VPN, you could log into that and your computer would think you were in Alberta no matter where you were.
If you are going to be in Canada, you should be able to log in with your cable subscription credentials to watch any of the national broadcasts.
It looks like 9 of the Flames' remaining 15 games are national broadcasts -- All 4 Saturday night games will be on HNIC, the 2 Monday night games will be on Hometown Hockey, and the Wednesday night game will be part of Wednesday Night Hockey. Plus, the home games against Seattle and Vegas are also national broadcasts.
You can see the breakdown here:
https://www.sportsnet.ca/nhl/article...cast-schedule/ -- any games without an asterisk are national broadcasts. This is from last summer, so it doesn't include the 2 rescheduled games in Chicago and Nashville, but the Chicago game will be national and the Nashville game will be regional.
It looks like 8 of the next 9 games are national broadcasts (the only one that isn't is next Thursday at San Jose), then 5 of the final 6 games are regional broadcasts (the only one that isn't is the final HNIC against Vancouver).
Then, of course, all playoff games are national broadcasts, so you won't have to worry about regional broadcasts if you'll be out of town in May/June/July.