Regarding bribes to the Policia, I was stopped once between Arequipa and Moquegua at check point. Of course, being gringo's we were told to pull off to the side for further investigation. After a lot of back and forth, the cops basically told us to give them all the money we had. Being cooperative sorts (and out numbered) we dumped all of our soles on them (probably about $10-15 US) and were were let to go on our way. Luckily, they didn't think to ask for our American money of which we had a considerable amount!