When you are in another country and speaking the language of that country, is the correct etiquette to also speak with the appropriate accent, eg. French, or are you supposed to use your own accent?
If you want to be understood, you should try to speak as much like native speakers as possible. What you call a French "accent" is simply the way French people speak. Many English people think they will sound funny if they try to imitate the French - eg by rolling their r sounds. In fact, it's quite the opposite - to the French, they sound funny when they say French words in an English way.
I believe the actor who played the German officer in the tv series 'Allo Allo' who spoke with English a strange accent used to tour schools to demonstrate that his accent, and the strangled pronunciation he gave, is what we sound like if we speak French or German, but without the correct accent - faintly amusing.
However, only perfect your accent if you're good at the language. I once practiced my German phrases until I sounded exactly like the tape - and then because everyone thought I could speak German OK, the reply was very difficult for me to understand. My English accent usually raises a smile, it apparently sounds pretty funny, but it warns the other guy that I'm only a beginner. However, at least I'm trying. To me the height of rudeness would be to ask first if they spoke English.