Does it have to be a plan? You could just get a 4G SIM, from Telecom Personal for example, keep it topped up (they automatically deduct 27.99 Pesos per day for a 200MB allowance per day) and you have a pretty good data connection. You can manage the subscription via the "Autogestion" page. I get between 20 and 50Mbps downlink on Speedtest in Palermo.
It will fall back to 3G if 4G coverage is poor, but that's generally not an issue where I am.