Andorra has no airport and no excuse for discovering that after you land. You fly into Barcelona–El Prat or Toulouse–Blagnac, then take Andbus, Autocars Nadal, or a winter ski transfer up the valleys to Andorra la Vella and Escaldes-Engordany. The first language on the street is Catalan, then Spanish and French; Portuguese shows up in shops because that is who staffs a lot of the retail.
Duty-free electronics and perfume are the old joke; the better trip is Grandvalira or Pal-Arinsal in winter and the Madriu-Perafita-Claror valley or Caldea's spa complex when you want to be indoors. Euros are legal tender even though Andorra is not an EU member. Mountain weather turns a July hiking day into a jacket afternoon without asking.
Andorra Telecom is the network in the valleys. Coverage follows the road and the resort; it is not a promise on a lonely ridge toward France. Install data before the bus leaves Prat so the driver pin, the hotel on Avinguda Meritxell, and the next bus to Pas de la Casa are on the phone in the tunnel, not after you find café Wi-Fi in Escaldes.