is served by both the LUAS lines (plus a walk) and a number of bus services. See the official site for info:https://crokepark.ie/getting-here
LUAS info and timetables on the official site:https://luas.ie/operating-hours.html
Bus routes and times:https://www.dublinbus.ie/Your-Journey1/Timetables/St Stephen's Green
is less than 3km ( 2 miles) from Croke Park
so walking would also be perfectly feasible.