Thanks guys.

I checked with a couple of providers in the U.S. and I'm really surprised by the lack of reasonable international voice and data plans in the US. I'm not surprised by the non-existence of such plans in Canada because there isn't enough competition in terms of providers and the costs of cell phone services have been sky-rocketing from the beginning... I really thought they would have cheaper options in the US:(. Maybe I didn't look up the right providers though.

Yes, I'm familiar with Skype, but I need to have a mobile phone so I can answer calls even when I'm out of the RV. I will look into that SIM card option to see if it is doable and if I can get a no contract voice and data plan that isn't too expensive. The MiFi looks awesome, but it would definitely be too expensive for me: $300 for the device (that I might use only for a 3-4 months period) + a no-contract plan for the MiFi + a phone (or a new SIM Card) + a US phone plan + my existing $55 plan in Canada.

Thank you all for the leads:)
Gen