Most Icelanders speak excellent English, so you'll have few problems if you don't know any Icelandic. However, any attempts to speak the local language will be much appreciated.

It helps to be able to pronounce place names with some degree of accuracy, even if they are long and littered with unfamiliar letters such as Ɖ/ð ('eth') and Þ/þ ('thorn'). In anglicised spellings, Ð is often replaced with D, Þ with Th (so you may see Seydisfjordur in place of Seyðisfjörður, Thingvellir in place of Þingvellir).