Hello ... I'm going to go in a month, so it's not high season, like in summer, it pays to pay the ticket to visit both parks (island and universal) ..

Cool

you can, but you won't be able to enjoy everything and you will get very tired from all the walking. I just got back in January and I'm so glad I had two days because I was so tired at the end of the day and that was just one park. so if you want to enjoy everything, do both days and if you upgrade when you arrive, you will get two more days for free if you buy from an undercover tourist.

If it refers to visit the 2 the same day, I do not think it's a good idea pq are 2 large parks with many attractions and there are always queues ... Now if you buy an express line it may be a good idea

If it is very good only that being there you have to pay the Express to pass quickly in some do not let you go up without that pass

Always!