We did Delta to SJU out of ATL with 8-9 hr layover in SJU.... Left ATL about 630 PM and SJU about 1015 PM.... To SJU Airport Hotel and slept several hours before 7;00 AM flight.... no Taxi Time! Arrive EIS and at TMM on Sea Tiger by 0830.

And if round trip doesn't seem to work well, check Multi city with return trip out of STT as another option.

SJU was clean and comfortable. Not luxury but Location great! Early morning flights seem to be less likely to be delayed, especially weather delays. And the extra layover allows any delays on the front in to catch up before the SJU to EIS leg.