NPH provides a wonderful home for children who have had a hard life. The volunteer program is a great experience and you really make a difference for the children. You will form amazing relationships- guaranteed! I volunteered in 2008. When I was there, the volunteers worked 10 days, then had 4 off to travel, relax, whatever. The volunteers live in the NPH home, but have a separate house. Free room and board is a huge plus of this program compared to many I found in Nicaragua. There are volunteers from all over the world, but mostly the US and Europe. The other volunteers are great support because they are going through the same issues you are adjusting to another culture and being away from family and friends.
During a normal weekday, you would spend the majority of the day doing your "job" - English teacher, tutor, therapist, etc. The late afternoons and evenings are spent hanging out with the kids in their homes. During the weekends the volunteers often help plan games and activities for the children, as well as simply spending time with them reading, playing cards, or watching movies.
The Nicaraguan home is brand new; the children moved from the old location on Ometepe in 2009 and 2010. Some non-essential buildings are still being constructed, which makes it an exciting place to be. Every time I go back to visit there are new changes. The new home is already very nice and the changes just make it nicer. The home itself is completely safe.
Nicaragua is a great country that is very welcoming to travelers. The NPH home is located in a great area for travel. The buses are cheap and you can go all over the country. Nicaragua is actually a pretty safe country. It's important to take normal traveling precautions, but I never had any problems in my whole year there, or in any of my other trips to Nicaragua before or after.
Overall, I completely recommend this program to anyone looking for a volunteer opportunity that really makes a difference for kids. Plus you can stay connected to the organization once you get back. I sponsor a girl I worked with during my year of volunteering, I've helped out with fundraising events, and I've returned to visit. You really become part of the NPH family.