My dog is free to run around if there aren't so many people nearby.
When there are not many people around, we don't put our dog on a leash.
ご質問ありがとうございます。
① "My dog is free to run around"＝「私の犬は自由に走り回れます。」
"if there aren't so many people nearby."＝「もし近くにあまり人々がいなければ。」
② "When there are not many people around,"=「あまり人が周りに居ないときは」
"we don't put our dog on a leash."＝「首輪を付けてはいません。」
ご参考になると幸いです。
アメリカ合衆国 
