The official language is Lao and it is written in Lao characters. Older people and even the educated younger people might also talk France and the latter one also English.
The official currency is the KIP but for tourism most prices are quoted in US$ and US$ are in many places also accepted. ATM's have found their way to the main places and the more expensive hotels will also accept your credit-card.
There is no rail-road network, although there is a train going from Thailand to Laos (just crossing the border). There are about 15 official airports (but not all are always operational) in Laos so there are domestic flights, mostly operated by Lao Airlines. Flying is safe in Laos.
As in other SEA countries roads have improved very much in the past years and travelling over land has become much easier, although going up real north the roads are becoming a bit less good (or sometimes even bad). Be aware of the fact that Lao people consider the road to be part of their place to play and live. Avoid travelling at night.
Be aware of the fact that it seems that time has passed Laos and then I mean time as in clocks. Lao people are not in a hurry and everything goes slow. So take your take and take that in account when making up your travel plans in Laos.
Laos has all kind of hotels & guesthouses. From the simple guesthouse with shared bathroom up to 5 star luxury resorts. Hotels in Laos tend to be a little bit more expensive (for Asian standards) for what you get for your money. Even in remote area's you will still find hotels, but more the kind of "lodging" places. Simple and cheap.