Our daily trip today was to Punta Negra.
There is a large beach over there, some restaurants and even hostels. However what I noticed compared to previous year they have raised the prices nearly by 50% for food - it is quite insane. Chicharon de pescado s/45, it was s/30 last year!
The water was also very dirty. Seems lot of gutters are drained just into the sea in that area. Lot of dirty yellowish foam floating on the ocean. The sand contains lot of garbage, apparently they never sieve the sand like on major beaches in EU. No life guard though.
The only advantage of that place is that it is not really crowded even in the summer. So if you can live with all the garbage it is one of the closest places to Lima that is not overcrowded.
Btw the traffic was horrible. Around 12pm took us 1.5 hrs to reach the beach from Surco - for 37km distance it is just insane.