God's law and the truth must be publicly witnessed. We cannot shrink from our duty to let sinners know their ways are not those of God's or ours. The rosary, signs, pictures or passages of scripture are all appropriate. Those that are open to the message do not discriminate between Catholic or Protestant or Jewish belief in life.
And at protests opposing abortion all completely ineffective so they are inappropriate. I know many devout and holy Catholics who feel similarly.
The above is a complete TURNOFF to many people who are open to prolife opinion but who may not share the Catholic faith and for that reason is also a TURNOFF to many prolife Catholics who might be otherwise willing to participate in prolife events.
I myself would prefer to protest against against abortion, the way I have protested for or against other issues.