should I sue?

Today my GF was driving down a street at 30 MPH and saw a "Dip" sign with no speed limit attached. The sign was located at the dip not ahead of it to warn drivers to slow down. She launched her Saturn and it came down so hard it broke the oil pan. Fortunately she is sharp enough to pull over and inspect the car and found the oil pouring out. She called AAA and when the tow truck driver showed up he said he gets 2 or 3 calls a week for a tow from that spot. I told her to call the city and raise hell. I also told her that there is probably some bent front end parts and it would definitely need an alignment. I also advised her to file a claim with her Ins. Company. She was driving the speed limit and using "Due care".