I have the Kickstart plan with Sprint, its $25/mo and also works free abroad for SMS and 2G data. In the USA its unlimited data LTE. Calls are cheap abroad if you need it in a pinch. It's valid for a year, some say you can renew it, others say after the year you get rolled to a regular plan, so you'll need to keep an eye on that. I activated it on my iPhone (you have to call them) then can swap out GSM sim's as I like. Put the Sprint one back in and it works fine. Here's the Slickdeals thread: https://slickdeals.net/f/13124116-sp...archBarV2Algo1

I'm sure many will extol the virtues of Google Fi, it might be just what you're after, although I think its just a tad too expensive as a daily driver ($10/GB while Kickstart in USA anyway is unlimited). I can't imagine having Google Fi and staying under $60/mo.