mobile phone & data package

Kerry, Galway and Dublin is a wide net, and I can't say that one provider will be better than all others in all 3 locations .... but, as a lifelong O2 user, I have spent time in all 3 areas and have had no trouble with coverage (unless I was in a cave, or deep in a concrete basement car-park). I suspect all major providers (Vodaphone, Eircom, 3, Meteor) will cover all those areas.

A Pre-Pay plan is the way to go, that way you are not commited to a contract (if they even give you one, as you are a visitor).

As for O2, they have a plan at the moment, where you credit €20 (per month) to your balance, and they take €10 and give you free phone calls to all networks and landlines. You then get an option to 'buy' 250 text messages for €5 (taken off your remaining balance). So, for €20 you can get free calls and 250 free texts and still have €5 left over ..... not bad! O2 do have a Data plan for €20 a month, but I dont use it, so I dont have specific details. Check out their site => http://www.o2online.ie/o2/shop/plans/prepay.php

If you make a call from your mobile to another mobile (regardless of the location of you or the receiver) you will be charged a mobile-to-mobile rate (its one rate if its from your network to the same network and a different rate if its from your network to a different network),
If you make a call from your mobile to a land-line (ie a phone in Kerry, Galway , Dublin etc) you will be charged a 3rd rate (ie mobile-to-landline), regardless if you are in the county you are calling or not.

So, keep an eye out for special packages and plans, as they all offer something for free , and charge for something else.

Lastly, depending on where you are coming from, I would reccomend you go with the local version of your own provider, if possible. IE if you are with Vodaphone in UK, then get a pay-as-you-go sim from Vodaphone here, so you can avoid (un)locking issues.

PS hope you enjoy your stay!!