Not related to the Falmer, but rather the mer we know exist - the Dunmer, Bosmer and Altmer (excluding Orsimer as a bit atypical, Maormer who are rarely seen, and the half-blood Bretons). Assuming we'll be able to play as mer (given past TES games, it is almost inconceivable that we won't), would you like there to be a climate of hostility towards merfolk, including the PC?

In Morrowind, the xenophobic Dunmer of Vvardenfell were hostile to all outlanders, including fellow Dunmer - calling them Outlanders (among other things), which becomes a quest point when trying to fulfil the Nerevarine prophecies.

Skyrim was the first point of landfall for men (bar Redguards) emigrating from Atmora, the Nordic hero Ysgramor and his Five Hundred Companions (whose names are still chanted) drove out the mer, establishing the first kingdom of men on Tamriel. Will the Nords of modern day Skyrim remember the Night of Tears, and how the merfolk destroyed Saarthal, the first human city in Skyrim? Or have old rivalries been forgotten - after all, nobody gives mer in Cyrodiil a hard time, despite the Ayleid atrocities.

The PGE, 3rd Edition, suggest that tensions linger in the closing years of the 3rd Era:
"The struggles between the two - prototypical men and prototypical elves - continues in some form or another to this very day...
...In the centuries that followed, Skyrim expanded and contracted as battles were won and lost. Though Cyrodiil was considered a separate domain, the Nords and the early Imperials formed a loose alliance against their elven opponents, their cultures mixing together, creating the foundations of modern day Aedric worship."
http://www.uesp.net/wiki/Lore:Pocket_Guide_to_the_Empire,_3rd_Edition/Skyrim

The 1st Edition suggests that much of Skyrim remains isolated and embraces a uniform Nordic tradition and culture:
"The northern and western Holds -- Winterhold, Eastmarch, Rift, and the Pale, known collectively as the Old Holds -- remain more isolated, by geography and choice, and the Nords there still hold true to the old ways. Outsiders are a rarity, usually a once-yearly visit from an itinerant peddler. "
http://www.uesp.net/wiki/Lore:Pocket_Guide_to_the_Empire,_1st_Edition/Skyrim

How would they react to a mer walking through their village? Hackdirt all over again? A Morrowind style approach, of general distrust and xenophobia? Or a very noticeable hatred of elves?

Personally, I'm hoping this is addressed - it will add to the flavour of Skyrim, and add value and a different feel to replays.

It's hard to say.

On Solstheim at least, the Nords and Dunmer seem to have put aside their old differences (as of The Infernal City). As for the other Mer, and Dunmer on the mainland... I'm hoping for the Morrowind-style general distrust.