The best place to arrive is Sacramento (SMF), because it is the closest to Davis, but you can also fly into either the San Francisco (SFO) or Oakland (OAK) area.
Supershuttle or Davis Airporter from Sacramento to Davis would cost about $23 for person. If you book a round trip, price will double, but there is an opportunity to get a discount.
If you chose to fly into San Francisco, you will lose more time. You will have to take a BART to Berkeley, which will cost approximately $8. After one-hour trip you should take BART to Amtrak, and from there you will go to UCD. Road from Amtrak will take about 80 minutes and you should spend $24 for one-way ticket. There might be other options to switch to Amtrak, and you can you use them too. Whole way would cost for about $30, so you won’t have an option to save money. As far as you can see, Supershuttle from San Francisco will have approximately the same price, but it is much faster.
If you want to use another shuttle to Davis, you have to book it beforehand.
The train also remains a great option, because you can work during the way to UCD, and it is very popular among UCD workers who live in the East Bay or San Francisco. The Amtrak station is right next to downtown and it is placed near all the mentioned hotels, so it won’t take much time to get there.