I was imprecise when I said "book" as I really meant to say "hold".

That said, I put both on hold as a oneway, called AA to see if I could merge them and, indeed, I can. In addition, the agent also got me an astoundingly better fare.

My original fare was LAS-JFK-SJU in F for $630 (yes, F on the 762 seat 3D) redeye so I could get some sleep and then an S fare SJU-MIA-LGA to get back to NYC for about $190.

She found me a fare for the LAS-JFK-SJU part of $395 in F!!! she merged the two legs and it priced out at $585 plus the ticketing fee. Looking at the reservation, she did change to SJU-MIA-LGA segments to O fare so there goes any AABRN credit (probably doesn't matter as I probably will get 5 RT's that qualify anyhow).

AAmazing!