Sorry that my answer is in english only. There is (better: was) no Audio-Guide available in spanish. But befor you go to Hiroshima ask for "Hiroshima Peace Volunteers"; there might be someone who speaks spanish.

Suggest you ask someone (or use Google ruteplanner) which trams you should take from your cruise terminal to the A Dome Memorial / Peace Memorial Museum. Trams in Hiroshima works very well. You get on and pay to the tram driver when you get out. It is fairly cheap.

The peace park and dome are open to the public -although you can’t physically get into the dome. The entrance fee is for the museum only

It says Spring 2019. The exhibition is now installed in the east building. Would be nice to know how the difference is, once it is open. I already found the temporary version quite well-made.

You can get there by electric rail or by bus. Buses only take exact change, but you can use your pasmo card or, if you have a JR pass, get on the red tour bus (FREE WITH YOUR JR PASS!) and it will stop at the most popular tourist spots. Most people don’t realize that it’s included. Google it for details...

L'ingresso costa 300 yen circa €2.50.

I would say definitely the museum and a walk in the peace park and, depending on your views, you may find something in the ruined hospital at the A-Bomb site. It wasn't for me though! There are some nice tranquil parks and temples to see too. I hope you enjoy your time in Hiroshima.

The Hiroshima Peace Museum Staff will give the best answer to your question, but almost certainly you don't need to book tickets in advance. While at Hiroshima make sure to spend half a day (or more) visiting the Island of Miyajima - get a train to the wharf, then a short ferry ride to the Island. More than enough to see and do there, even without bothering to take the cable car to the highest point.

Yes. It’s open on weekends as well. You can choose the language on the website. Yes. Weekends are open as well. If you have a chance, please go there.