By public bus: From Guatemala City to Iztapa from the bus terminal in zona 4, 05:00-18:00 more or less every hour, 1 hour and 45 min, boat across the canal of Chiquimulilla to Puerto Viejo, and from there by bus to Monterrico four buses a day. Or by bus to Taxisco, another bus or pickup truck to La Avellana, and finally a lancha boat to Monterrico. If you don't want to boat you can now as of Nov 2008 at least take roads totally over-land in any combination of bus, mini-bus or mini-van all the way to the main intersection in Monterrico. There are also 3 direct buses from Guatemala City to La Avellana, leaving the bus terminal in zona 4 may have moved as of Jan '08? at 10:30, 12:30 and 14:30 check the schedule with Transportes Cubanita.By shuttle: From Antigua you can take a direct mini-bus shuttle for US$18 round-trip which leaves at 8AM and returns at 3PM daily.
By car: Head for Escuintla - Puerto Quetzal - Iztapa - across the new bridge opened October 2007 to Puerto Viejo - and then to Monterrico. Or you can take the Carretera al PacÃfico from Escuintla - Taxisco - La Avellana and a ferry to Monterrico.