Dalarna is an important province in the history of Sweden. Several uprisings against foreign and domestic rulers have occurred. The most famous is how Gustaf Vasa, the last remain of the Swedish noble after the Stockholm Bloodbath, hid in Dalarna when the Danish were looking for him. Here he sought support amongst the locals for an uprising against the Danish who now had occupied Stockholm and thereby the control of Sweden.
Swedish is of course the main language but you will find that the vast majority of the locals speak English very well, although possibly (but not always) with a strong Swedish accent, which is one of the most distinct accents in Europe. Unlike in many other countries, even older people do usually have a decent command of English; people who don't speak a word are extremely rare.
Flights to Borlänge go from Stockholm, tickets can be booked online at the site of the airline Skyways . Borlänge can also be reached by air from Malmö, Gothenburg and from Oslo, the capital of Norway. Tickets online at Direktflyg . There are also domestic flights to Mora from Stockholm. Tickets available online at the site of the airline Nextjet . All airline sites have booking services in English.
Most cities are reachable by rail, tickets can be bought at the website of the Swedish railway company SJ .
Going by bus is usually slightly cheaper than by train. You can buy tickets at the website of Swebus Express  (Available in english).
Travelling by bus within a city costs 17 SEK (12 SEK for children below 16), and the ticket can be used multiple times in one hour. If you are younger than 20 years old, you can buy a card called "Upp till 20"(Up to 20). With the card you can travel with bus anywhere in the county, even between cities, for a month.
Most cities and towns in the county are connected to the railway-network.
There are dishes from all over the world available at restaurants. Domestic and international fast-food companies are well established.
There is nothing in particular to watch out for. Pickpockets may sometimes appear in crowded areas, such as popular markets and shopping-malls. Altough if you'd ask an local they'd probalby be hard pressed to remember ever hearing about that kind of stuff.