Upvote:3
It is a fundamental principle of European Union freedom of movement that EU citizens can use national ID cards, such as the Portuguese CartΓ£o de CidadΓ£o, to travel to other EU or Schengen countries. With your national ID card, therefore, you need neither a visa nor a passport to enter Bulgaria.
You will of course need to exit whatever country you are in at the moment, for which you will probably need a passport. If you do not have the proper documents to leave your country of departure, you will be unable to board your flight. The specific documents you need will depend on your itinerary.
Similarly, you will also need a passport to travel outside the EU. If, when you leave Bulgaria, you are traveling to a non-EU destination, you will need a passport and possibly a visa to enter the country, and therefore also to board the flight.
The only perplexing thing about your question is the report that the Portuguese embassy in the UAE told you you would need a visa to travel to Bulgaria. It's possible that your speculation that they don't "have a clue" is correct, but it's also possible that there is some policy or practice of UAE exit controls that creates a requirement for you to have a visa. I can think of two ways to resolve this; neither is particularly satisfactory:
Ask the Portuguese embassy in UAE to explain why you need a visa. Then take that explanation to the Bulgarian consulate and see whether they will issue a visa. This solution is likely to be unsatisfactory because, as you say, the Portuguese embassy is "very very slow."
Just make the trip with the documents you have and see what happens. This is obviously unsatisfactory because there's a risk that you won't be able to get to Bulgaria in time given the uncertainty about the documentary requirements.