I have written about half a dozen articles about Roam Mobility. They offer the most competitive US cell phone service for Canadians traveling to the US. They have always been the cheapest option but they cut their prices in October.
There is a group of Canadian retirees that heads to various US sun destinations in winter that the media calls Snowbirds. Now Roam Mobility has a plan for these Canadians traveling to the US for longer than 30 days. You get all of the standard Roam Mobility goodness of unlimited calling to Canada and the US, unlimited text messaging, US number, voicemail, Caller ID and 1 GB of 4G data for only $39.95 a month. The only condition is that you must purchase this plan in blocks of 3 months.
Source: Roam Mobility Snowbird Plan