FO Pay
$9.43 per duty hour for FO pay. Pretty brutal but they justify it by saying FOs are (usually) not required crew members. You get bumped off a flight if its fully sold out which hurts the flight time. And during the busy season in whichever region you are in, it can get old fast. But, you can ask around in the hub of other captains might allow you to tag along in the right seat on a round trip you weren't originally scheduled to make up for it.
As far as SJU or MAZ as an FO, chances are better for SJU. Depends on what they need at the time of each bid...