Sure, you can fight it. It's impossible to tell whether you will win... but if you don't fight it, you're sure to lose.
California requires proof that you actually drove the vehicle while intoxicated to convict you of DUI. The prosecution might argue that having the keys in your hand is circumstantial evidence that you drove, but that might not convince a jury.
Remember, you must contact DMV, and request a hearing, within ten days of a DUI arrest or your license will automatically be suspended. The DMV action is completely separate from the court case... and it is usually too late if you wait until the court date.
Most DUI lawyers will handle DMV proceedings as well as the court case, and they can make sure your rights are protected.
A no driving defense is one of the strongest for a DUI case. There is no proof of driving and you have a witness that will say you were not driving.
The answer to your question is YES, you can fight this DUI.
You should find a DUI lawyer who is familiar with the court you will be attending. Make sure he or she is a member of the California DUI Lawyers Association and the National College of DUI Defense, and that most of their practice if not all is DUI defense.
Make sure the DMV hearing is requested within 10 days of your arrest. That 10 days includes weekends assuming the weekend does not fall on the 10th day.
The investigation... or the lack thereof... may be your best friend in this situation. They have to prove driving. Not only that you drove, but when you drove and that you were under the influence or that you were at or above a 0.08% at the time of that driving.
Did they even check to see if the car was warm? Cold? Condensation on it? Things like that - things you would expect them to do in the investigation - if they didn't, it could lead to reasonable doubt when coupled with witness testimony, bar receipts, phone records, etc.
But you're going to need an attorney to do this - it's not going to be a do-it-yourself project.
Don't miss the 10-day window to request the hearing with the DMV.
A roundup of the best tips and legal advice.