As the posters here have mentioned, it is best not to take symbols superstitiously. Symbols have power because of the reality they represent.
My real question is this: if you believe in the power of the symbol of the cross, then do you also believe in power of the reality of the cross? By this I mean, do you believe the sacrifice of Jesus has real power in that it moves God to mercy towards us.
Because if you believe that then you have the whole gig figured out. The best ‘cross’ is sanctity. The best shield is one’s baptismal seal. I say this with no prejudice to you-- I don’t think that you’re an automatic target because you aren’t Christian, but I do think that Christians have a certain special protection because they participate in the victory over Satan which Jesus won.
If you’re going to get the cross or crucifix blessed because you believe in the real power of that which it symbolizes, then I definitely recommend that you get one and get it blessed (even if you don’t accept all the Christian beliefs). But if you’re going to view it as a superstitious item-- as magical-- then I recommend that you don’t.
In the meantime, please take the time to pray to God and ask Him for that very protection which you seek. Cultivate a relationship with God, even if you can’t be in a religious tradition.
I was reading a passage out of the prophet Jeremiah which I think is illuminating. God is condemning the Israelites through Jeremiah because they have forsaken him for foreign powers and idols. He says:
They who say to a piece of wood, “You are my father,” and to a stone, “You gave me birth.” They turn to me their backs, not their faces; yet, in their time of trouble they cry out, “Rise up and save us!” (Jer 2:27)
I think this is a peculiar situation which most of us have found ourselves in at some time or another. I’m not any different. We don’t have any relationship with God and we live our lives in a way indifferent, and even antagonistic to him. But, when trouble comes and we need His help we run back to Him like children. “Rise up and save us!”
I’m not trying to accuse you by this; I found this illuminating as to how I act. I think it reasonable to believe that we can’t expect God to work things out for us exactly how we like if we refuse to enter into a loving relationship with Him.
So I definitely recommend prayer as your first resort.