Trinity is probably your best bet [during academic term] on a Tuesday evening. During the summer time, practice tends to move outside to Merrion Square. Trinity has a good collection of props [juggling clubs etc] and you don't need to be a student to get in. Trinity meets in Goldsmith Hall, which is on the corner of Pearse St and Westland Row, on the same "block" as Pearse Station.
UCD has always been a bit more variable with locations and times, so I'm not sure about the current state of affairs.
DIT: to be honest, I'm not sure about how easy it is to get into the practices (my knowledge was prior to the Grangegorman campus).
DCU: I don't know if this is still running. They did have an amazing selection of props built up quickly as they had extremely generous funding - but they always had major issues in that you really had to be a DCU student to attend.
If you are on the north side [or if you have easy access to the Maynooth train line] you may also want to consider the Dublin Circus project which has a new building in Cabra (beside Broombridge train station).
Also look out for the Dublin Circus Festival [which is essentially a juggling convention, but there's more funding sources if its called a circus festival] which is in March.