Advice on Hotel Location in Paris

I would suggest somewhere in the 5th (Latin Quarter) or 6th (St. Germain) close to the river and the St. Michel fountain. You would then be near the RER B that goes to the airport and the RER C that goes to the Eiffel Tower. It is a very central area that will allow walking to many things and it would also give access to multiple metro lines.

We stayed in Monmarte 20 years ago when we visited friends. We liked that location though it was a bit outside of central Paris. A few weeks ago we stayed in Clichy which is on the west side of Paris just at the outside edge of the ring road. I would not recommend that area especially for woman. Maybe it was the neighborhood our hotel was in but we saw instances of disrespect towards woman and my wife was never comfortable walking to the metro in the 3 nights we were there.

For lots of reasons, I would not recommend staying outside the Boulevard Périphérique like John did. For two full days, staying in the Latin Quarter or Le Marais would be great. I don't think the 6th has the vibe that I think you are looking for based on your asks. Outdoor music performers is an interesting ask. I'm not sure where to recommend where you would be guaranteed to see them at any given time in Paris, especially if you are not going in the summer. You might want to take a look at this https://www.discoverwalks.com/blog/top-ten-places-to-watch-street-artists-in-paris/ By chance will you be in Paris on June 21st? I like the Oberkampf 'hood for just hanging out and people watching but it is not the quaint Paris that many visitors want: https://www.timeout.com/paris/en/things-to-do/republique-and-oberkampf-area-guide and it is not within walking distance of the sites that you mention.
When you say easy access to the airport, do you mean by mass transit or by car? If the latter, most places will be the same level of ease, give or take a few minutes of travel time on a Sunday morning. If you mean by mass transit and if you do not want to have to change trains, stay near Saint-Michele-Notre-Dame, Luxembourg, or Gare du Nord stations. I just don't think the people-watching is the greatest near Notre Dame station unless the people you want to watch are tourists.

The Latin Quarter between metro Cardinal Lemoine and Place Contrescarpe had the vibe you're looking for when we were there in May 2015. We stayed at Hotel des Grandes Ecoles in Rue Cardinal Lemoine and absolutely loved it. It's an easy walk to the Ile St. Louis and Ile de la Cite, too.

For airport transfer, we used Paris Webservices, recommended in Rick's book (you get a discount if you show your copy of the book to your driver). The car was nice and new and clean, and the driver spoke good English and was very helpful

When we are leaving for CDG from Paris we stay at a little place in the Latin Quarter just steps away from the RER B, that goes straight to CDG. It's called Hotel Jardin du Luxembourg. It's on a quiet dead-end street, right across the way from the Jardin du Luxembourg, and an easy walk to St. Germain for the cafes and music you seek! Super laid-back. Stayed there many times. Nice front desk staff. Rooms at the front have cute little balconies with views over the rooftops.

Thank you guys SO MUCH for the input! We got a little hotel in the Latin Quarter super close to the Luxembourg station. Easy walk to Notre Dame area and EXCELLENT people watching. Super easy to get to hop-on-hop-off bus. It was so nice to have the RS community once again save the day for us.....it's like asking family! Thanks again, we had success due to your suggestions!

Isabel,

Will you share the name of the hotel and a short review?

We just got back home from Paris. We stayed at a Air b and b that was a house boat on the seine. We were literally a 5 minute walk from the Eiffel tower. It was a great houseboat, plenty of room and very reasonably priced. Much cheaper than a hotel. Next summer when I go back I will try to book the same houseboat.

We went with Hotel Cujas Pantheon. Simple and TINY, but excellent location and clean and safe. Would have been super helpful to know that it's now called French Theory, so there is no HCP signage anywhere (except all the booking sites online). It was a winner and recommended!