@Shran
There are portions of highway with 80mph speed limit if the Prius will do it in Montana. (Just moved a buddy back from Houston, the U-haul truck wouldn't do 80.)
Cdn speed limits are in km/h, Highway 2 from Coutts to Calgary is mostly 110km/h: divide by 2 (55) and add 10% (11) to get mph (66)
Be aware there are 2 seasons: Winter and Construction on the roads.
As was noted, you will need your passport to cross. Be nice to border agent and you will get through quick.
Make sure you clean any weapons out of car (even pepper spray is considered against the law).
You are limited to 1 liter (basically a fifth) of alcohol each, and carton of cigarettes (if you think gas is expensive, you should see cost of smokes).
Note: PBR would be expensive import beer; flat (24) of Molson Canadian, Eh is only $40, here in Calgary currently.
Liquor sales in Alberta have been privatized since some time in 90s; they're open 7 days a week from ~10am to 10pm. (You do still have to go to liquor store)
If you're coming to Banff, you probably want to drive up the road a little ways to Lake Louise (~35miles). The lake is gorgeous. (It is glacier fed so water is...brisk at best.)
If you golf, there are some very nice courses.
If you hike and/or bike, there are some excellent trails If you and missus are really adventurous, I could loan you my tandem mtb for a day.
Be prepared for any weather - it can be 32 or 90 or both in same day.
If the locals are carrying winter jackets, pay attention One of my staff, up from LA, went hiking and was almost a casualty when weather changed from 90 and sunny to 30 and snowing on a June afternoon.
Our summer rains are usually short but intense (and occasionally include hail) .
In Banff, there are often wild animals (especially close to golf course). They have the right of way.
e.g. High capacity assault elk
Every year someone tries to get too close for a picture and makes the news...
I've never had any issues with bears (only seen 2 in ~25 years I've been going to Banff).
Cell phone coverage is good along highway and in town. But there are no towers in the park = no service (I love it that no one from work can get a hold of me when I go out on trails)