Taxi cabs should be hired only from stands in the airport, at major hotels or at major intersections. Zona 1, Guatemala City's downtown, is its oldest section. It houses all the budget hotels and restaurants. It has a solid reputation for muggings and robberies and is unsafe for walking after dark. Be on guard with your belongings in the day time as well.
Lets have a little faith.
There is no single central bus station in Guatemala City . In coming passengers are simply dropped off on a busy but dim lit street in the downtown area of zona 1. From there you are on your own. Like bats in the night in search of moths , swarms of taxi drivers with sharp radar skill, circle the incoming buses. Each driver ready to pounce down on the first of the red eyed travellers stumbling out the door into a humid jungle of tar trails and fire breathing behemoths.