Hi Rookie...
Six times as both a teen and an adult, I have traveled to the indigenous Tarahumara within the rugged and pine covered mountains of the Sierra Madre Occidental in Chihuahua, Mexico. This was a tremendous experience. However, it was quite a bit of work! We worked from before the sun came up until after the sun went down.
I traveled with a non-denominational minister from Texas. He gathers doctors, carpenters, skilled workers, interpreters and volunteers to travel in either late October/early November or in the summer. It is an exciting time -- and every person is expected to contribute. We are expected to contribute via hard work and in verbal ministry (whether sharing their testimony or one-on-one evangelism).
Each trip usually involves some sort of building project (a church building, a well, a school, a clinic, etc...), medical projects (vaccinations, dental work, etc...), and educational/philanthropic work. Those who go are asked to raise the funds in order to help complete this task. It can cost upwards to several hundred dollars, and we end up "roughing it" in terms of accomidations. I have usually slept on floors or outside (or if you are particularly blessed, inside of a vehicle). There are almost no opportunities for a shower during these 10-14 day trips, and the food is mostly confined to camp food.
I have also gone on several easy "border trips" in Mexico. More times than not, these trips are almost "tourist-like" in nature as they are confined mostly to the poverty regions along the border. We usually are allowed just a little time of evangelism in areas already saturated with the Gospel. While these might have some merit, they aren't exactly my idea of true "ministry" in terms of sharing the Gospel. While those trips are far easier in regard to accomidations and work, I never found them as fulfilling as the more difficult trips into the mountains.
The Tarahumara were so receptive of the Gospel. They literally live in caves high in the mountains and far from normal Mexican civilization. There is no electricity, no running water, and the people live much like they would have a thousand years ago. Most do not speak Spanish, and most have never traveled beyond the rugged mountains that our 4x4s have taken us. They are animists who believe in many different gods. In those difficult trips into Mexico, I have seen many people (including adults and fellow teenagers) who felt that their lives were immeasurably changed by these difficult missionary trips. I know several of the young adults who actually went back and stayed working at these locations for six months!
Anyway, I recommend that you find a good ministry to work with (yes, [u]work[/u] with). The tourist-like "quick evangelism excursions" that are often reflective of large "safe" ministries are okay, but I have always found the purpose-intrinsic trips to be far more fulfilling.
:-)
P.S. - I have several friends who have participated with "Global Expeditions." Each of their stories were similar. They complained of an extremely "structured" mission setting with quite a few participants who don't go for the right reasons. Each returned with mixed emotions, complaining that the expedition "could have been better if..."