I must say that I find more Catholics during street evangelism than any other religious group out there. When you talk to Catholics just take them through the Law, it works beautifully. A lot of times Catholics know very little about their doctrine and the Bible so they are some of the easiest people to talk to, not that they are ignorant but because they have no objections, they usually always agree with you. Just take them through the Law and then go from there.

Watch out for people that try to talk about purgatory. This is a made up idea by the Roman Catholic Church that tries to explain where people that have not heard about God (i.e. people in Africa or other countries) or people who are "good" people but have not accepted Jesus' sacrifice will simply go to so that they aren't punished in Hell. The Bible says nothing of this so don't waste time dealing with it.