I think I might lean more with Angband on this one. My personal opinion (pure flight of fancy, I'll admit) is that Elrond could be reading/purusing a letter/message from Galadriel. For all we know the message could be brought by Haldir, which would explain why he shows up at Helm's Deep with a message from Rivendell. This is just my interpretation of the scene- I don't particularly expect anybody else to go along with it.
As for Elf telepathy, there was a lot of discussion on the book boards during the summer comparing Galadriel's mirror with the palantiri. Personally I think the 'technology' behind them is very similiar, and the mirror could probably be used for long-style communication.
Also, at the battle in "the Black Gates Open" Sauron is able to immediately send for the Nazgul in an attempt to thwart Frodo. Perhaps if the big baddy can do this, some of the Elves can as well.
What news from the South, O sighing wind, do you bring to me at eve?
Where now is Harad the White? He tarries and I grieve.