Suzanne:  It really depends on how much you plan on making use of public transportation. If you were to get a Navigo card, you'd be able to buy two one week passes (they go from Monday to Monday and then would probably want to buy carnets for the subsequent days.

People are now allowed to use one ticket on a bus trip if they transfer within 30 minutes.You can get all over the city with one metro ticket per trip.

I usually use carnets - and occasionally will buy a one day pass and do each and every one of my errands on that specific day.

Paris Visite Passes aren't really economical because they give you access to three zones and it's rare you'll travel in more than two.

This is my opinion.  What do other people think?

I think the Navigo is great. Not good for everyone because of when they arrive and depart and how long they stay. I go often and stay for at last a month. I usually load it weekly, but my next trip I will be arriving perfect to load it for a month...cheaper that way.

The convenience is that you can hop on/off buses or metro wherever and whenever..get on and off every block if you wish to. You don't even have to take it out of your purse..just pass purse by the spot! I might walk one way and return via bus. It is very convenient.

Joan