How widely is Mandarin used in Nanjing? I know there is a Nanjing dialect of Jianghuai Mandarin but I have not been able to learn much about current usage in the city of Nanjing.  For example, do many people in Nanjing today ordinarily begin words with an "l" sound where standard Mandarin has "n"?  Do many people in Nanjing today use a very different vocabulary than say people in Beijing?

I am considering travel to Nanjing, and I wonder how well my Mandarin training will suit Nanjing and whether Nanjing usage will conflict with my training.  (I speak French with something of a Montreal accent, which causes more amusement than misunderstanding in France.)
Nanjing has a very good education environment. Most of the famous universities of Jiangsu province locate at Nanjing. So Mandarin is wildly used in Nanjing and most of the young people are well educated there (this means they can speak English). They may speak Nanjing dialect with their parents and friends, but they can also switch to Mandarin as soon as they find you are speaking Mandarin. Additionally, my hometown is a small city adjacent with Nanjing and our dialect is very close to Nanjing dialect, but I found both these two dialects are quite close to Mandarin. So just go there with your Mandarin, don't worry! (I know little about French but I still went to the Quebec city last year!). And If you found some trouble, ask for help to the young people there, they can speak Mandarin and even English!

By the way, the 'l' and 'n' issue you referred is true about the dialect. However, most of Nanjing people won't do this when they are trying to speak Mandarin seriously.