When I was 16 I went to Germany for 2 months and worked at a barn there. It was insane and overwhelming, but definitely worthwhile. I had the time of my life, worked with some amazing trainers and horses, learned A LOT, and made a lot of memories.
You had better be prepared to work HARD. Most Americans think that it's going to be a nice trip and they are going to have such a great time, and they are very surprised when they realize how much work is expected of them. It's no picnic in the park. The work wasn't really a problem for me, I've been a working student for my trainer for years, so I am used to the long hours.
It will really break you down. I was constantly fighting to prove myself, and it is really hard to find out just how little you really know when you are so far away from home.
I would reccommend it, but only to extremely hardworking, dedicated, determined, and quick witted riders.