You’ll have every Saturday and Sunday off, plus a few vacation dates scattered throughout your semester. Usually, it works out to be around 9 days off from volunteer days (in addition to your free weekends). You will not know your travel dates until you arrive in-country; your school and your Local Coordinator will figure out your vacation dates.
Usually, semesters have a couple of 3- or 4-day weekends, plus a longer vacation that may be around 5 days off from teaching (plus the time off you get on the weekend, of course).