The official language is Spanish, but various indigenous communities speak Quechua, which is also considered an official language. English is spoken in almost all tourist areas. You will get a better exchange rate at the banks, and there is one at the Lima airport. Travelers Checks are difficult to exchange. Bring cash for small towns and villages.
Weather conditions vary from season to season and region to region.
For the Highlands, the dry season is from April to November. For the Coast, the dry season is from November to April. Coastal temperatures are usually very mild and vary little during the year. The highlands can be very cold at night time. In the jungles, the dry season is from April to October.