The reason for the testing is because adult Jews are responsible for carrying on the traditions to the next generations. So in order to be sure it's done so correctly, they train you & test you.
I guess if you want the responsibility, then you should train hard for it, for such training should also continue on throughout the rest of your life.
I will admit I haven't heard of many Spanish Jews. Here's a question though: have you thought about checking into Messianic Judaism? These are Jews as were the Apostles of Jesus Christ...they're Jews, they follow the traditions handed down to them, continue with all the ordinances and such, but have accepted Jesus as the Messiah. That, in my opinion, is also the purest form of Judaism. Just a thought.
I've not done it yet, but I'm excited for when I do. Nervous, yes, but it's something I really want so I'm not going to let anything stop me
Just try to relax, and realize that if you are sincere, the rabbi will realize this and try to help you a lot.
And there definitely are Spanish and Latina/Latino Jews ! Aliza Hausman (she has a blog), on here there is Friendly Jewish Accountant (but she's not been on in a really long time) and many, many others.
answer: I know a Latina convert on this forum (and among my contacts)
Don't worry about the test - its an "open book" final, so to speak. The rabbi wants to know that you have the basics down and will work with you one-on-one on parts you're weak in.
It isn't scary at all, I found it an absolute delight and I am the ultimate house-mouse.