Been there several times.....You MUST have a gps if you are going out into the boondocks (which is most of Ireland). The 'signage' is horrible, even the locals complain about lack of signs (ALL signs, directional signs, street signs, etc.) Or you can do what we did on our first trip without a gps, get lost a LOT and then stop in at a pub and have the inhabitants argue amongst themselves for 10 minutes (at least) as to the best way to get somewhere. At least the draft Guinness was good. Also, get ALL the insurance you can. The left side of virtually all rental cars look like a pissed-off tiger clawed the hell out of them, the roads are so narrow you WILL be running up against the hedgerows (if you're lucky, if you're not, the rock walls will get you). When we got the rental car and noticed how beat up it was, we had the agent note it on the contract - after she gave us a look of "What???" IOW, if you DON'T have the insurance you will be paying for everyone else's damage. While I have greatly enjoyed our trips over there (the wife has relatives on the west coast) you REALLY better mind your p's and q's on the narrow back roads as often the clearances are TINY. I've driven all over the world and am a decent driver (did SCCA stuff back in the day) but I would not recco driving in the boonies of Ireland unless you have a gps, good nerves and quick reflexes (have had to bail out into driveways,etc a couple of times when a tour bus took up half of MY lane (and the speed limits are often ridiculously high for the conditions). You'll be fine as long as you avoid the temptation to take your eyes off the road at the wrong time (which is hard to do as the scenery is amazing, as is the people and the food). Enough said, you get the picture. Have fun!!
ps Go to the Beatty Library near Dublin Castle, voted European museum of the year but little known, a cabbie insisted we go there and we're very glad we did. Also the Guinness Factory is fun.