Hi,
"Villa Caracol" on a little road ("Calle Chicago Boss") off the beach (809-240-6078) is about $30 or less, is clean, with ac, fridge, hot water bath and security box, no tv in room, small restaurant downstairs. Particularly nice Dominican people run it; in super quiet setting about 2 minutes walk to the beach.
If you go there please mention I said hello. (Actually I hate to give this little pearl away, but they do deserve more business.)
Bests, Skip