I highly recommend Inlex/CA, especially if you are considering a combination learn Spanish / volunteer experience.
From arrival at the airport in Guatemala City to my departure three weeks later, I was extremely well looked after. I never was concerned about how to get anywhere, how to do anything, or any other aspect of my stay, because the staff at Inlex/CA assisted me with every possible logistical detail and eventuality. The support is second-to-none.
One of the main reasons I chose Inlex/CA for my experience was because I wanted to learn Spanish, and I certainly was not disappointed. During my three weeks, I truly had an authentic immersion experience. With the support of the Inlex/CA staff, my incredible host family, an amazing one-on-one Spanish teacher (a total of 60 hours), and the staff at El Centro Sabor y Gracia, my Spanish went from beginner to advanced in only three weeks.
The volunteering aspect of the programme was also rewarding. I was able to teach English to a small group of primary (age 5 - 8) students, and another group of junior (age 9 to 12) students at the Centro Sabor y Gracia in Santo Tomas. The director and staff of this special project were also very supportive, and the children, although energetic and with a wide variety of learning needs, were responsive and appreciative of the time I spent with them.
The locale (Santa Lucia, Santo Tomas, and Antigua - the #1 tourist destination / jump-off point in Guatemala) was small enough to present an authentic picture of daily life in Guatemala, but it also provided close access to many popular trips around the entire country.
Inlex/CA really did give me the experience I was looking for; it effectively catered to both aspects (volunteering and learning Spanish) of my three-week "holiday."