Edward does it all the time at L40.... he plays a month and then drops it a month... then plays again when something new comes along.
You'll need to call Account Services at 877-427-7744 to cancel the account. When your ready to re-activate, if you think you'll be doing the on-off thing make sure you only do it by Game Cards or Monthly Subscription so you don't end up paying too much.
Before you go cancelling that account though - remember to a) have a slot for a low level ship open, cause you'll need to buy one (with all ships locked except for Light Sloops and Light Galeons - you'll need a spot to buy one) and b) with only the Cutlass, Pistol and Doll (and very limited) be sure you have them set up the way you want them (remembering that only the low level attacks are open to you).
Finally - no worries on re-activiation, everything returns to normal as soon as you activate again
See ya on the seas Rabbit