Verizon roams off of Telus and Telus has nation wide coverage. Telus/Bell actually now have very impressive coverage and depending on where you are, you'll get better coverage than with Rogers/Fido (at least I do on my Telus phone - I always get greater coverage than my boyfriend who is on Rogers).
So long as you don't intend to use tons of data while you're here (avoid streaming music, downloading apps, etc.), you'll be just fine. And as others stated, Verizon has a great North American option that they can get you while you're here. When you add all of this up, it is far better than dealing with the hassle of unlocking your phone. Canada is not Europe and your CDMA Verizon phone will work just fine here.
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