Great beach-bars walking distance from Playa Blanca - Rojo, Mata Chica, Portofino and Costa Maya.
I know the latter two (Costa Maya / Portofino) will be open all September. Check dates for vacation closings on Rojo and Mata Chica.
Mata Grande Grocery has a fun weekend bar-b-q and cold beer.
In San Pedro the usual places rock - Fidos for night time fun is a must .... but just show up and follow the music & laughter, you'll find a good time.
Food -- oh my, will let the rest of the boarders post on that subject - the recommendations will be many and good.