Thanks Guys for the input so far.
I guess I should have said, I am in Ireland and will fly into a major city to start the trip - ideally not too much travel from there to get going. Not sure I could handle trying to get the bikes onto multiple flights, it proved difficult before!
I think we would like to end the trip in a big city to do some of the normal touristy things during the trip as well.
I am glad you both mention the North anyway for this time of year as a good option - I wasn't sure the weather would be OK, though obviously hard to predict...
I will look at both your suggestions tho, I loved New England when I was there years ago and always liked the open, sparse, empty nature of the US Russ! So different from home.