Many can speak English, with varying degree of fluency.
USD is very widely used in Siem Reap- so no need to exchange local currency. Vendors (even the roadshow mineral water seller) will quote in USD.
Cambodia is a country still very deep into poverty. That is why don’t feel upset if you have to pay USD1 for a big bottle of water from the street- they need the money to survive.
As you approach tourist areas, street peddlers start following you coaxing you to buy things. Many of these peddlers are young children who can converse in simple English. Buy from them instead of from tourist shops. These children need the money so much more.
Begging is a common scene you will see and the locals will know that you are a tourist at a glance. If you give to one kid, you may find suddenly many would appear.
Unlike Sri Lanka whose people love souveniors from Malaysia, Cambodia people are more interested in $$.
