I'm not too surprised at the amount of people here in Antigua studying Spanish. Guatemalan Spanish might just most understandable that I have ever encountered. Their speech cadence is slower than most Latin Americans and they speak clearly and simply. No puzzling colloquialisms, no chopping the ends or beginnings off words (I'm looking at you Chile and El Salvador), no slurring or messing the words about (costeños!), just pure, easy-to-understand Spanish.
Oh, and the going rate for 4-hour lessons, 5 days a week: $90