carlam,
i think it depends who you are going with and what type of vacation. I have been to a few beaches on the coast of Argentina. I went to Mar de Plata with friends and San Bernardo/Pinamar with my boyfriend. Mar de Plata and Pinamar were very busy, Pinamar being much more pretty, but if you are looking for relaxing and not such a huge nightlife, San Bernardo and that area is pretty cute.
