I don't know if this helps, but when I was in Mexico recently, I was surprised how much I ended up using free wifi connections, rather than having to use any network based data access. Though I did end up in quite touristy places, even the smallest cheapest hotels even in small towns had decent fast wifi, as did many restaurants and cafes. e.g. as far as I know, all the inexpensive VIPs chain of restaurants have WiFI, and they are in hundreds of places all over the country: See
VIPS. Mostly WiFI was locked and often provided by a bigger company like Telefonica, but I was always given a key when I asked for it after ordering a drink or food. Also I often picked up open "free" wifi in many street locations. (obviously less secure...)
Perhaps touristy areas of Guatemala are the same? I would think so. They are very similar countries.