Road biking is a fairly popular sport in Guatemala [1], particularly in the highlands, where mountain roads offer unique challenges to strength and endurance. The country even has its own version of the Tour de France, known as La Vuelta Ciclística a Guatemala (The Biking Circuit of Guatemala). The event takes place yearly sometime in August.
More popular with visitors, mountain biking is increasingly popular in the hills around Antigua [2] and Lake Atitlán thanks in part to a number of excellent local outfitters.
Links:
[1] http://www.moon.com/destinations/guatemala
[2] http://www.moon.com/destinations/guatemala/antigua