No! I signed up alone and had never met any of the people that were going to be in the same group as me. If you want you can sign up to go with someone you know but personally I think it makes the trip more fun to go alone because then you get to meet new people.
During my trip, they ensured safety by having mentors and group leaders supervise students. They also had students travel in groups for things like the bathroom. We were almost always under the supervision of the staff and when we weren't, we were in groups. Safety pertaining to the program was not an issue when I went abroad this summer. I hope this helped!
Teens ages 14-19 are eligible to participate.