We just got back from 2 weeks in Spain and 4 of us shared Skyroam, the mobile wifi.
It was perfect to share and allowed us to be connected wherever we were. When we were at apartments/hotels with wifi, we could access that, but if we were wandering around, we had connectivity on the go.
For making phone calls, we used WhatsApp. I think we only had to make one dialed call.
Highly recommend! The cost is $10/day if you rent the device and $8/day if you purchase it for $100. Split among two couples, it was quite the deal.