If I rent a car and don't pay for that extra liability protection. Do I expose myself to a dangerous amount of risk?

I'm a 23 year old guy working for the Navy. I'm in San Diego. I want to rent a car for a week just to get off base. My car is in storage in CT and I don't have active car insurance. I also don't have a major credit card. My question is, assume the worst case scenario. (i.e. I accidentally hit somebody, god forbid), how much risk am I exposing myself to financially?