Yes Portugal would be a good choice because of the sun, very cheap land and labour. And actually the Portuguese speak good English, better than the Spanish anyway, but you still have the skills problem.
There are rumours that the Gigafactory in Nevada has had problems because of a lack of skills. People just don't know how to work in a Gigafactory. It has the word "factory" in it, but it is mainly a software engineering plant. Outside of California, software engineers are scarce and in Europe, very scarce.
The skills problem is rarely talked about. In traditional car factories, you just need people with arms and legs who can lift stuff and learn a simple skill after watching someone for a day or two. That's not the case when you are building smartphones on wheels which are constantly being improved and new innovations happening in real time.
If Tesla wants to be a company that continues to innovate at all its Gigafactories on everything they do, this business model seems super difficult to me. I think a better model would be to have an innovation centre at Freemont/Nevada and then the other Gigafactories will simply "copy" what the guys do over there i.e. the Chinese model. Heck, maybe the software engineering for the Portugal Gigafactory could be done remotely in the US, and you staff it out in Portugal with robot technicians/maintainance guys. That may be more realistic. You could train one of these guys in maybe a few months...