Don't have a conniption fit, jeepers
You can go to Guaycanes (sp?) between Boca Chica and Juan Dolio for a post-George demolished town with no services ( rental umbrellas included from what I could see) with a few very nice beaches or you can go to Juan Dolio and use theirs, that is, the beaches that are not all taken over by the 75 AI resorts, that is.
You just keep going east from Boca Chica and there are turn offs/ exits for them both. You'd need a car or taxi or get off the gua-gua and hoof it to the beaches. For the sake of the cost of an umbrella this seems extreme, mind you.
As for "overrated" if you are sitting on a beach, with your chair and umbrella , rented or not and reading, a beach is a beach really, sand, water, people.