The best way to book tickets with JetBlue is to go on JetBlue Bestfarefinder site. Also a great way to gauge ticket sales. Looking at the next three days here are the number of unreserved seats:
The Embraer 190 has 100 seats (25 rows of 4) for a grand total of 600 seats. Right now 72 seats (32 + 40) equates to an 88% load. Now keep in mind that of the 72 seats, I bet you at least half are sold but passengers have not checked in yet to reserve their ticket. In other words, the 88% will most likely be more like 95%.
Check out these two stories about JetBlue: