Expats pretty much can have Nicaraguan friends, especially if they are Caucasian because Nicaraguans like Caucasian people.
I am not certain as to the reason why they prefer Caucasian people but I think it is because most of the people here have brown skin. There is no resentment whatsoever given the hostility between the two countries in the past.
Titles are quite important as well, so pay attention when making introductions and address people using Don for men or Doña for women, followed by the surname.
Panama's two coastlines are referred to as the Caribbean (or Atlantic) and Pacific, rather than the north and south coasts.