My wife who used to work with llamas, among other animals, assures me they can be ridden by adults, easily carry packs, and are quite pleasant when properly raised. Yet, in everything I have read about their use they are never used for transportation either with teams pulling wagons or by being ridden. Am I just not aware of their use as a riding animal, or were they never used in that way?
Your wife is correct that Llamas are docile animals that can easily carry packs, but they are to small to be ridden by adult humans. A typical adult llama may be 5 feet to 6 feet five inches tall at the head, but they have long necks and are only three to four feet tall at the shoulder. They can carry up to 25 percent of their body weight as a pack animal, but few llamas exceed 400 pounds. Most can carry 80 pounds over distances of 5 to 13 miles per day. Llamas do have one advantage over horses, they can climb and decend stairways that would spook most horses. Llamas are well adapted to the Andean high lands, but their thick wool makes them less suited to the hot deserts of the west coast of South America. They were the primary transport animal of the Inca and earlier highland Andean cultures.
Source: http://www.llamasofatlanta.com/llama_facts.htm