I did the RYA competent crew out here in Barcelona with a company based in Brighton.
I had 0 sailing experience.
Before the course, I brought Dummies Guide to Sailing and buried myself in the book. It helped to have some basic knowledge of how sailing works.
The course was great and as other have said, you'll be getting your hand dirty. I went on to do the Day skipper 6 weeks later, and am now the proud owner of my very own boat.
Still learning every time I sail though :)
It's a very well put together course and an excellent starting base.
I did mine with lagoon.co.uk