Just returned from Carnival Glory 7 night from New York to Halifax. Halifax was 88 degrees.
I have personal suggestions.
New York - we stayed one night at The Verve Hotel and taxied into Times Square and took the red hop on hop off bus tour. We didn't get off. We got off where we started, ate dinner, and returned to take the night light tour of New York. These were very different tours. Being unfamiliar with getting a taxi, we waited in front of a hotel until one dropped someone off and got in.
I highly recommend the Verve, clean and very friendly staff. It included breakfast.
Boston - used the green double decker hop on hop off tour busses ($23 for seniors for basic 2 1/2 hour loop). Great tour and for a little more you can add extras like a boat tour and walking tour of Harvard (voted best tour in Boston).
St. John - had fog like pea soup, but not cold. We did a city bus tour, $20 cash, and we could see the reversing falls, but that's about all because of the fog. They stop at the market and reversing falls for restrooms. We were met with a rose for the women and a lapel pin for the men. Very helpful ambassadors if you have any questions. They directed me to the city tour bus. It only operates when ships are in.
Halifax - It was 88 degrees. We walked out of the port and there was a line for taxi tours. Very easy. We went to Peggy's Cove and someone had fallen. You will see why when you are there. Be very careful. When we returned the whole city had lost power, so we didn't go into the Citadel. We never heard why. We walked back down to the water and along the boardwalk. Lots of places to eat here. We had a lobster roll and a beaver tail (a pastry with any topping you want from apple pie to chocolate and m&ms). Some in our group who just walked straight back to the ship felt it was too long of a walk. Just a head's up if you have any mobility issues.
Portland - if you are doing the Portland city and Lighthouse tour, 105 minutes, you walk out of the port and turn left. It is about 3 blocks, depending on which pier Norwegian uses, on the same side of the street, $22. If you like architecture this tour is loaded. I had our tickets on hold and they filled up quickly. Phone number for this company 207-774-0808. You can also buy beaver tails here just past the bus. They are 1 hour ahead of ship time, so be aware of that so that you aren't late.
We did each port on our own and saved a lot of money.