The last hurricane season in the Atlantic was anemic, being one of least active periods on record. This was attributed to extra dust blown off the Sahara which inhibits hurricane development.
Right now, the various forecasting agencies around the world are agreeing that there is a greater than 50% chance, perhaps a 70% chance of an El Nino event happening this year, starting in the Summer or Fall. Traditionally, we think of El Nino events as inhibiting tropical storm and hurricane formation in the Atlantic. Today, a group that predicts hurricane activity in the Atlantic every year has used the likely El Nino event to predict that this year's season will be relatively low level.
According to this prediction, there will be nine named storms in the Atlantic, three of which will become hurricanes, one of those a major hurricane (Category 3 or above), with a 35% chance of a major hurricane hitting the US coast somewhere.
Personally, I'm not sure about the effects of El Nino, should it occur. There haven't been that many El Ninos during the period for which there are high quality records. This year's El Nino, if it materializes, will occur during a period when we are experiencing strange and different things in the Arctic. Many of the teleconnections between El Nino and other conditions elsewhere in the world are highly variable and many are not all that well understood. Overall, with global warming, conditions may simply be different enough this year from any other prior year that predictions may be off. While it makes sense that if there is an El Nino we should expect an attenuated Atlantic hurricane season, I'm not going to be surprised if several of the usual links between El Nino and various weather conditions are different than "usual."
The standard explanation I have heard for why El Niño years tend to have fewer Atlantic hurricanes is that during El Niño events upper level wind shear is increased in the tropical North Atlantic. You are correct to note that we are in climatologically uncharted waters, so we shouldn't count on this correlation to hold. And even in an inactive year, hurricanes will form and sometimes make landfall, so anybody near a vulnerable coast should make preparations. But we don't know yet exactly how things will be different--maybe this correlation will hold, and a different one (e.g., El Niño years usually mean wetter winters in California and the southern US) will break. So hope for the best, but prepare for the worst.
Also, hurricanes may be weaker this year because of relatively cooler Atlantic waters. But an El Nino should do some planet-wide warming up. So, an El Nino may actually increase hurricane activity, just in a later year.
Still clutching at straws, I see...
The local fishing industry along the affected coastline can suffer during long-lasting El Niño events. The world's largest fishery collapsed due to overfishing during the 1972 El Niño Peruvian anchoveta reduction. During the 1982–83 event, jack mackerel and anchoveta populations were reduced, scallops increased in warmer water, but hake followed cooler water down the continental slope, while shrimp and sardines moved southward, so some catches decreased while others increased. Horse mackerel have increased in the region during warm events. Shifting locations and types of fish due to changing conditions provide challenges for fishing industries. Peruvian sardines have moved during El Niño events to Chilean areas. Other conditions provide further complications, such as the government of Chile in 1991 creating restrictions on the fishing areas for self-employed fishermen and industrial fleets.
The difference here is that there is an observed and modelled physical mechanism (wind shear) associated with the correlation, e.g. the house bets heavily on a light hurricane season if El Nino emerges.
More on El Niño and hurricanes:
Excellent post on El Niño: