In your home country, the Visa Signature benefit functions as secondary insurance. But I assume the reason you're considering this is because you're renting in a place where your primary doesn't cover you. In that case, read the fine print: the Signature card might be a good option as its exclusions are pretty limited (Jamaica, Israel, Ireland).

I'm kicking myself for not using it in Mexico. I plunked down the $30 for CDW just assuming that all credit cards would ban Mexico from their insurance. This one doesn't.