This is exactly what we do too. Claro had a campaign for prepaid sim cards, we bought two... I believe the 140 pesos for 5 days is not unlimited as such, it was like 5GB with full speed and then it drops, or something like that.
We have also the wifi boxes from both, Orange/Altice and Claro, and use the same prepaid sim cards on the wifi boxes, works perfectly. From Altice you get 7GB data with full speed for 139 pesos and from Claro as said above, 5GB or unlimited for 5 days. I find that the wifi box catches the signal slightly more efficiently, and provides wifi strong enough to stream on multiple devices at the same time...