If you only have 2 days, then stick to Dublin itself and don't bother with renting a car. The rest of the country is well worth seeing but you can't do much in 2 days. If you're dying to get out of town, try a day tour to Glendalough or maybe up to Newgrange.

To eat, I'd hit Gallagher's Boxty House in Temple Bar and order a boxty, which is a potato pancake filled with stew (beef, lamb or chicken). It is also the only place in Dublin you can get Murphy's stout, which is Cork's competition to Guinness. For a quick bite, try Beshov's on O'Connell St for great fish and chips. Order for a side of curry sauce to dip the chips in.

As far as tourist sites go, it depends on your preferences. If you like to drink a bit, the Jameson Tour is OK, but the Guinness tour is probably more interesting, although the brewery is a bit of a walk from the city center. Many visit the Book of Kells at Trinity College and you get to see the library there too, which is impressive. There are also a few museums in town that have ancient artifacts that have been dug up from all over the country. And if you're the literary type, you can go on a James Joyce tour and see the sites from Ulysses.

There are so many pubs you won't have trouble finding one. Famous ones include Doheny and Nesbitt's, Davy Byrne's, and the Brazen Head, which is almost 1000 years old. Stick to Guinness or whiskey. Once you open your mouth and the locals hear your American accent, you will be inundated with new friends with all kinds of questions and stories. The best part of Ireland is the people you meet, not the sights you'll see.