4 hours is more time then I'd typically want to hang around in SJU, but given those options, that's what I'd go with. 1:10 is probably enough time, if everything goes well. If you are late at all, then it can become a problem. With the 4 hours, you have plenty of time, even if there is a delay. And since your 5:30 flight is Cape Air, it is possible you might be able to get on an earlier flight if there's room. So doing that, I'd go check in with Cape Air first thing and then see about food after depending on what they say about flights.