In Chosica, the central plaza area has lots of restaurant options, such as El Fondo Marino which has decent seafood and also Don Alberto Resturante, which serves a variety of different food.
While in Chosica, check out the ruins of Marcahuasi - a minor and slightly bumpy road leads from Chosica to the ruins, which are a series of rocks which resemble different shapes, including a large face, various animals and a sleeping Incan! There is a trek up to the site from the town of San Pedro de Casta, but as Marcahuasi is 4,000 metres in altitude, give yourself time to adjust before starting the trek. Or you can take a horse or donkey up to the site. Tickets are 10 soles for foreigners and 5 soles for locals.
Hope that helps.
Have a good trip!
South American Explorers,
956 Enrique Palacios,
Tel: 01 447 7731http://www.saexplorers.org
Open: Mon-Fri: 0930 – 1700 (Weds: 2000); Sat: 0930 - 1300