How much time free time do you usually have, if at all?

It depends on how you set up your schedule of you're volunteering, taking Arabic lessons, or both. You'll go on trips with the center, but you'll also be able to go places with your host family. I found that I had a comfortable amount of free to do the things I wanted to.

Your primary role as a volunteer is to teach and assist at the center, but I found myself with a lot of free despite the classes and Arabic lessons I was taking. The lessons are not onerous, and even though you have only 2 days off (1 week day of your choice and Friday) you can manage to still do quite a lot even on the days you are working. The center organizes a lot of trips and outings, and a lot of locals are very excited to show you around. One of my pupils drove a truck as a side job, and he offered to take me on one of his trips once - we went to 3 different cities across the region. Beyond that, I managed to do so much during my time at the center - I went on numerous tours across the area, visited many different cities and still worked as asked for at the center. You just need to be proactive in how you want to spend your time at the center; they're very understanding peopl

Like the other answers said, it depends on your schedule, and how much teaching you want to do. While I was there I taught 2-4 1.5hr classes Sun-Thur, took 2 1.5hr Arabic courses each week, and had plenty of time to explore Hebron and other cities.

Also the staff is very nice so if you, say, want to go to Jerusalem on a Wednesday and you let them know ahead of time there'll likely be no problem.

I have had a lot of free time. Sometimes less because you are planned in for courses as a teacher. But there is a lot of freedom in asking free time and enjoy yourself in an other city or with friends.