Considering 2 nights in Dublin, take train to Belfast for 1 or 2 nights, then take bus to Dublin airport to pick up rental car for the rest of the trip (5 or 6 nights in the west and south - Cliffs of Moher, Dingle Peninsula, Kenmare, Cobh).
Visiting the Titanic sites is not a priority for me. Definitely want to take a Black Cab tour. Is it worth it to go to Giant's Causeway or should I balance the trip with more city time? If we don't do G.C., is 2 nights worth it?
Thanks!
Given the high cost of rental cars at the moment you'd be well advised to minimize the time that you actually need one.
One suggestion would be to take advantage of the RyanAir direct flight from Dublin to the Kerry airport near Killarney, from where you can collect your rental car for explorations around Dingle and the ROK before heading north towards Galway, dropping your car there once you've seen what you came to see, then catching the train back into Dublin. There are two flights per day connecting Dublin & Kerry - one in the morning and one in mid-afternoon - taking about an hour as opposed to the long drive.
Doing a one-way rental between Kerry & Galway will save you both time and money, and any drop charge will be more than offset by the money saved by booking the car for fewer days.
You could also do the reverse, ie train to Galway to collect your car, drive down the coast to Kerry, then drop the vehicle there and take advantage of the afternoon RyanAir flight to get back to Dublin airport before your return flight to the US. Might save a few steps and generally streamline your logistics somewhat.
Edited to add: we enjoyed our time in Belfast - it's a beautiful city, with a fascinating history, and the center is pedestrian friendly if you just want to meander and explore. It's one of the few places where we did the HoHo bus tour to get an oversight of the city and generally get our bearings, then struck out on foot for those attractions that particularly appealed to us. Point being that I think a full day there (2 nights) would be time well spent.
We spent a day in Belfast. The big sight for us was the Titanic Museum. It's one of the best museums I've been to. I'm not really a fanatic for either Titanic (the movie), the historical period or massive iron ships but I enjoyed the museum.
I'm not really interested in "the troubles" so didn't stay longer than a half day in Belfast. After the museum, we went a short distance to Carrickfergus Castle. After maybe a 30-minute visit we were ready to move on. We met a local couple with a dog like ours where we had parked. After a long conversation we moved on. We stayed at a B and B overlooking the coast maybe two hours from Belfast.
We stayed a night in Derry/Londonderry. Again, the troubles aren't interesting to me, so we mostly explored the walls and area inside the walls.
Our favorite sights were coastal views, small fishing ports/villages. Eating fresh seafood, strolls/hikes along the coast, ancient history (stone age sights) and staying in B and B's was our basic itinerary. Northern Ireland doesn't have the influx of tourists that the Republic has. To me that was enjoyable.
Maybe my single favorite site in the entire area was Grianan of Aileach. It's a ring fort. We went in the morning from Derry/Londonderry and were the only one's there. Technically, we were a little before opening hours but there is no gate or ticket booth, just a walk up from a dirt parking lot. To me it was evocative; it made me think of a different era of Irish history. It was almost like going to Newgrange and having the place to yourselves.
We rented a car out of Dublin for $6 a day (yes, I thought there might be a mistake) and drove at our own pace. It was their smallest car, with a manual transmission. When the car was ready. The agent said in a voice loud enough for everyone in the lobby to hear, "Who has a small stick?" I thought that was funny.
The highlight for us in Northern Ireland was a day that included the Giant's Causeway, Bushmill's Distillery, Dunluce Castle and Royal Portrush Golf Course (about a week before they hosted the British Open). The four are close enough that the day didn't feel rushed. As always, we slept and had breakfast at a B and B a little up the coast then moved on to another B and B a little way down the coast.
We spent 3 nights in Belfast, giving us essentially 2 1/2 days. The first 1/2 day we used to wander around, get oriented, and look at some of the architecture. The second day, we did a tour that included Giant's Causeway, Dunluce Castle, Larrybane Quarry, Downhill Demesne, and Ballintoy Harbour. I loved it and thought it was very worth it.
We had another full day in Belfast and saw a couple of the churches and would have liked to have seen Crumlin Road Gaol, but that needed to be booked in advance. Like you, Titanic stuff wasn't a priority for us, so we didn't do that. The Black Cab tour of the murals was an absolute highlight! We are still talking about it. I highly recommend Paddy Campbell Tours for this. http://belfastblackcabtours.co.uk See my trip report to learn why: https://community.ricksteves.com/travel-forum/trip-reports/countryside-castles-and-celts-croatia-and-ireland-trip-report-part-2-ireland
Happy planning. "It'll be grand!"
