Here´s another experience that might help you -
After double checking with the registry office etc, we were told that the tourist doesn´t need their passport translated but may require the photocopies to be certified.
You can request a date and time for the wedding a month before hand, online. Then the end documents tell you everything that you need to do in the week leading up to the wedding. As you are not from a spanish speaking country, the application online automatically asks for the name etc of the translator (without asking whether you are fluent or not). It will also ask for the witnesses´ information too.
The medical test HAS to be done exactly 7 days before the registry office date (you are given a list of places and the date on which you need to do it, but not a specific appointment time when you do the application online). It is my understanding that you can just turn up with the documents that you print off when you do the online application and the hospital will do the tests.