You can certainly fly to Buffalo, NY and cross Peace bridge. However taking a taxi is not a really clever option. Even though you are lawfully allowed to my knowledge, I personally wouldn't do it. My recommendation would be to rent a car at Buffalo airport and drive to peace bridge and back. Perhaps renting will also be cheaper than hiring a taxi back and forth and is also more comfortable. And I am not sure how the immigration officer at the port behave knowing you are just there to get it done and get out. You will have to provide an address for your PR card.It is always advisable to get into Canada at least for a day and get your SIN at least. You have gotten a PR. It is just nice to honor it. I am not trying to judge you and your option is perfectly fine and understandable, but I would recommend against it. And it is summer soon. It will be beautiful up there at this time. Think about it
Even though Canada lets you to get in and get out on the same day, the immigration officer at the toll booth as well may not be amused. I am not sure how many taxi drivers will be willing to cross the border with you. Remember he will also be required to do the immigration part unless there is a different clause for taxi drivers. I am not sure. For your not so much fan of driving long distance situation, a rental car from Buffalo is the best option. It is not too much to drive and is much easier, peaceful and enjoyable as well.
Also note the taxi driver will be the first one to talk to the officer at the booth. He will identify himself as a taxi driver. And then you do. This is unnecessary unless you won't drive at all. Rental car and all simple and easy. You can also drive to Niagara on Canadian side for the sake of it. It is fun in my opinion. May be even stay there for a night and then get back to Buffalo to board your flight back to Jersey.
