My husband and I are going to Ireland and London this fall the trip will be 12 days (including traveling to/from the US) the Original plan was to arrive in Dublin, catch a bus to Galway and stay there 3 nights then train back to Dublin for 3 nights before flying to London and staying 5 nights in London. However We are now considering staying in Dublin one more night and doing a day trip to Belfast/Giants Causeway on our last day and shortening London to 4 nights? Is Belfast/GC worth the extra night in Ireland vs London?

on a separate note does anyone know what transportation around Galway is like if we don't stay in the middle of the city how would we get from our hotel/BB to the main part of Galway to explore?

If at all possible stay in Galway close to the bus station so you can be close by for day tours.
Tons of B&Bs in Galway, just an example
http://angelas-bed-breakfast.galwayhotel.net/en/

I would go to Belfast and see the coast over a day in London hands down. The Black cab tours are very interesting or just a day trip to the causeway is worth it imo. I am going back for Belfast and the coast.

Yes I know Galway well (live an hour away) and public transport is fair by Irish standards but hardly world class. I always cringe a little when folk start talking Hotels outside the City. That generally means either on an industrial estate or out in the sticks and without the name of the hotel I couldn't tell you which.

Angela's given above is one of many B&B's on College Rd (I generally give Petra House) and walkable to Eyre Square if you are having a night at the other side of the city by the Latin Quarter you might want a taxi back?

Belfast and the Giants Causeway is great from Belfast. Personally I wouldn't do it from Dublin. But lots of people do.
You could fly to London from Belfast?

I personally would not do a day trip from Dublin. Belfast would be much better, so travel to Belfast, visit the Giant's Causeway, fly from Belfast to London.

I LOVE London (I visit at least 2 or 3 times every year) - but whether it is "worth" dropping a night in London to do this is really up to you.

If it was me, I'd cut a night or two from Dublin before dropping either the Giants Causeway OR London. I do like Dublin but there are about 500 X more things to see/do in London than in Dublin.

Can you rearrange things a bit and only do two nights in Dublin?

With several days in Belfast and a week driving around N. Ireland, I stayed a night near the Giant's Causeway and stopped because I was passing by. But I definitely wouldn't trade a day in London for it, especially since you have so few already.

It all comes down to personal preference doesn't it. Are you a city person (then London). Do you prefer the countryside and scenery (then Giant's Causeway). There is no correct answer.

I'd go for the Causeway everytime, but then I hate cities.

http://www.kennedycarr.com/day-tours/giants-causeway/

long day but what else are you going to do? I did it from Belfast but if you have no other option I would still do it. It is a UNESCO site for a reason. The bus tour from Belfast was full of stops and the scenery was great.

"Are you a city person (then London). Do you prefer the countryside and scenery (then Giant's Causeway). There is no correct answer."

I agree, there is no correct answer. However, I don't believe it's quite as simple as city vs country. I am, in general, a country sort of person but London is a special city. I suppose, considering the UNESCO designation, that the GC is a special landscape, but it isn't my sort of special landscape. And if I'd started the day in Dublin, rather than 5 miles up the road, then gotten to London realizing how many interesting possibilities I'd given to see it, well, I'd consider it a bad deal.

Belfast is a lovely lively city. I wish I had stayed there longer. I also enjoyed Derry, although it was much smaller.

To be honest, I had my fill of Dublin after two days and enjoyed Galway more. We adored visiting the largest Aran Island, Inishmore, and visiting the cliffs, Dun Aonghasa, from there. They were far more dramatic than the Cliffs of Mohair.

http://www.aranislands.ie/