Saludos @Doel Gonzalez:
A fellow Colegial here (ICOM '03).
What banks did you call in PR that won't lend to you? First of all, you are not a foreign investor. Puerto Rico is a territory of the U.S. and for all practical purposes it is treated like a state. I will suggest that you call the large PR banks (Popular, Oriental, FirstBank) to check. If you can find the time, it is best to go in person. In addition, check with the Savings & Loans ("cooperativas") since they are usually more flexible.
As to the DOS clause, it is enforceable, but as others have said the risk of it being enforced is minimal. However, there is a risk and the bank has the right (and the resources) to make your life miserable. Plus, you can get less than 8% financing right now.
If that doesn't work, you need to consult with an attorney. Some sub-optimal options come to mind, such as a long-term purchase-option which can be recorded in the property registry.