French is the official language, and all the locals will speak it. Some may use some non-standard expression, but most will make the effort not to use them if you are foreign.
Local expressions you might encounter are 'Tantôt' (Soon), meaning either this morning, this afternoon, tomorrow morning/afternoon or yesterday morning/afternoon, depending of the speaker, so ask for details. As Normandy is a premium tourist destinations, many of the younger people will speak English, and will be willing to speak it. Spanish, Italian, and German are also quite widely studied at school.
Although there are Norman languages, they are mostly dying out, and the speakers will also speak French. You may also meet the occasional speaker of the neighbouring regions' local languages, such as Breton or Picard, but in any case, a stranger would address you only in French (or maybe English if you were in a tourist area).
There is a ferry-port in Ouistréham, with ferries to Portsmouth with Brittany Ferries. Another popular option with the locals is the crossings run by LD Lines to Le Havre and Dieppe from Newhaven and Portsmouth, which are sometimes substantially cheaper. Cherbourg, Calais and Saint-Malo are also within driving distance.
Rail is the most commonly used public transport in France for inter-regional travel. It is cheap, fast and reliable. Check out reductions for under-26, over-25 and group travellers. Tickets can usually be bought abroad, on the internet, at stations; in advance or on the day.
Roads in France are good.
D-Day circuits are signposted, and take you around Normandy retracing the history of the 1944 events in the Region. Details can be obtained through the Official Site
France is a pretty safe country, and Normandy doesn't have any big cities with no-go areas, although as in any place, you should stick to a few obvious rules (don't walk down dark alleyways at 4 in the morning, etc...).
The European Emergency number 112 will also work.