I went through this agency to be an au pair in Spain for the summer. They are amazing!!! I was walked through the whole process from start to end. The application process is a bit extensive but that is how you know it is safe. The vetting process for both au pairs and host families ensures that both parties are comfortable. I was able to talk with multiple families and choose the one I thought was the best fit. The placement coordinator I worked with, Jelena Estrada, is absolutely WONDERFUL! She was so helpful with getting me through the application process and she stayed in touch while I was in Spain. Jelena was genuinely excited for me to become an au pair which made my experience even better.
If you're looking to become an au pair, Au Pair International is a great agency. I met other au pairs in Spain who did not go through an agency and they had a lot of issues. Some were being paid way under the legal minimum and others were even kicked out by their host family with no where to go. Going through Au Pair International meant I had a contract that ensured I was paid well and not fired without notice. It also meant I had multiple people I could contact if there was an issue with my host family. Au Pair International takes care of their au pairs.