The translation 'Dumas Avenue' is what I anticipated. But I dont think it is quite correct. One does not translate names of people or monuments, place names or even road names specific to their countries. I think it proper to leave it as 'Avenue Dumas', maybe without the article - this seem to be the convention.
Maybe you have heard of this: "The Three Musketeers (French: Les Trois Mousquetaires [le tʁwɑ muskətɛːʁ]) is a historical adventure novel written in 1844 by French author Alexandre Dumas. It is in the swashbuckler genre, which has heroic, chivalrous swordsmen who fight for justice." (Wikipedia)
Richard, please don't be such a pedant! The point isn't about the "the" - it's that I wouldn't translate Pierre's name into English.....because he's not. Therefore it should be perfectly OK to say l'avenue Dumas instead of "Dumas Avenue" and Duo should accept this. "English people", by the way, includes me. I'm English. I have been for all of my 54 years. That's why I'm extremely confused by your point about "the" - apologies but your use of commas makes it's very hard to get the gist of what you're trying to say. English people would say "where is The Avenue" to refer to a road called "The Avenue". They would also say "Where is Avenue Dumas" if the name were a French one. I suppose they might say "where is the Avenue Dumas" but there's no standard rule for this. I'm very English and I wouldn't say "the Avenue Dumas". Can you give me an example in context of what you mean as I'm confused. I would also order "smoked mackerel" or "the smoked mackerel" completely interchangeably. And to be pedantic (as I clearly am today as well ) if I were to use the definitive article for the road in question I'd call it "l'avenue Dumas". As in (in English to a french speaker) "Excuse me but I'm looking for l'avenue Dumas" as this is a road unlikely to be found outside a francophone country. Just for interest - do you speak English as your first language yourself?