Hello @scintillating: From my experience as an undergraduate, $20k for 9mon is a feasible budget. By feasible I mean you can easily live off this with planning and strict adherence to your budget. This will cover housing, utilities, gas, car insurance, cell phone, and food. It is tough to live extravagantly on this budget, but it is certainly doable. Davis is a town with a lot of deals and a lot of rip-offs. Some apartments, grocery stores, restaurants, and bars overcharge, while others offer awesome deals. Given that it is a true "college town" there are a number of shops that offer lunch specials or very great happy hour prices. I would stay away from any apartment complex owned by Tandem and attempt to find housing through independent property managers. I also recommend housing with others as it makes housing (the biggest part of a Davis,CA budget) more affordable.
Feel free to Direct Message me and we could talk over the phone sometime or something if that would also be helpful. Cheers!