I spent five months working mostly at the Casita de Madera in Villa de los Angeles just outside Huanchaco.
It was truly a life experience to be part of the daily life in such a non-developed society. I did really enjoy my time over there, but it would be like lying to say that everything functioned smoothly. You have to be prepared that this is Peru, not an industrialised well-functioning country. Some days non of your fellow staff members will show up, some days the kids wont attend school and sometimes you just don't have much to do.
But you can be sure that even if it might not feel like you are doing very much, the kids -and their parents- love just the fact that you are there playing with them, caring for them and spending your time at their kinder-garden, I felt really welcomed and the people in the village always had s smile on their face and some nice words the say to you.
It is really good to know Spanish, the more you know the more integrated you will get into your work. But you dont have to be fluent, the youngest kids dont care wether you speak spanish or not, just play with them and both you and them will have a good time! Another tips is to be creative, the resources are quite few but the staff are willing to improve the project so don't hesitate to ask questions and come with solutions or activity ideas etc.
If you want a really nice experience of working with amazing children and doing a difference in a quite poor community in south america, i would definitely think about working with Otra Cosa, you get the most out of Peru if you see the 'non turistic' spots as well, at the same time as you live in Huanchaco which is a wonderful little city right on the beach famous for its surfers, fresh fish for almuerzo and a touch of Chimu culture. A nice combination of being a volunteer and having vacation!