Glendalough is about 50 kilometres south of Dublin, a journey of roughly an hour by car via the N11 motorway and R763 through Roundwood. Parking is available in the lower and upper car parks, but both fill quickly on summer weekends and bank holidays — arrive early or use the bus.
St Kevin's Bus (stkevinsbus.com) runs a return service from Dublin city centre (St Stephen's Green) to Glendalough twice daily, year-round, with an additional service in summer. The journey takes about 1 hour 15 minutes. This is the recommended option if you're coming from Dublin without a car — it means you don't have to worry about parking or about staying sober if you want a pint in Laragh afterward. Bus Éireann also runs services from Dublin to Laragh, a 2-kilometre walk from the monastic site.