Hi Bridget
There are definitely ATMs in Cusco. I'm not sure about Puno - it's a smaller town than Cusco so they may be harder to find there.
As for spending money, you will need to buy around 12 meals but food and drink is very cheap in Peru. I would budget around £5-10 per meal plus a little extra for water and other drinks - maybe £150 overall for food and drink.
Kind regards,
Olly, your editor