Welcome to Dublin!
There are a lot of great caffes in the city center where the internet is quite descent. I’ve been testing for working some of those lately.
There’s KC Peaches on NE side of St. Stephen’s Green. It’s a good internet connection (although you need to reconnect every 30min or so). During lunch time it gets really busy and noisy.
There’s 3fe near Google. It’s probably the priciest caffe in Dublin, but the connection is good and apparently everything that you can order there to drink and eat.
Most of the Startbucks have good internet connection. Two of my favorite for working (they both are quiet almost the whole day):
(something’s wrong with gmaps links. One is rendered inline like a map and the other as link)
Note that Dublin has a ton of little hidden places like these. These are just some that I’ve tried out. If you don’t expect any calls, I suggest you try and explore a bit. It’s an incredible little city.