Some have said that maybe we should not witness at shopping malls. However I came across this verse that I think validates the practice.
“So he reasoned in the synagogue with the Jews and the devout persons, and in the marketplace every day with those who happened to be there.” Acts 17:17 (ESV)
The marketplace of Paul’s day was where the people conducted business. Today that is done in shopping malls, stores and other similar locales.
So, I think if Paul were alive today we would see him witnessing at the mall!