I am considering moving to Virgin because of the data option, but I have done exactly what you describe you want to do 3 years ago. I currently use Straight Talk, which is sold by Wal-Mart, run by Carlos Slim's telco (he's _the_ telco player in Mexico), which uses Verizon's towers. I pay $33 including tax for 1000min/ 1000sms (200MB of data, but it's ~useless CDMA 1.x).
edit: I don't know if you want VOIP opinions (there so many options), but I use flowroute and am quite happy with their performance/ pricing.