Beautiful but difficult for a non-French speaker
Most people prefer speaking in French and many do not speak English so this can be difficult. I would add though that most people I met were quite kind and patient with my poor French. As long as you are trying I think people will recognize your effort and give back. It's a huge walking city but I think if you have Google maps at your disposal, the metro and bus lines are quite helpful as well and will get you pretty much anywhere. Great architecture, beautiful people, rich history--lovely!
Insider Tip:Safe money by buying fresh ingredients and cooking your own meals. Also definitely eat cheese here and try the local fruit. It smells and tastes amazing. We don't have fruit like this in many places in the US.