Ulfchild, if it must be in Davis, I think Barbara's Dancing Tonight is the only one, but the last I check she had only one room, it's kind of small, and U-shaped.

If you don't mind travelling to Sac, The Ballroom of Sacramento on Folsom Blvd (right off 50) generally allows outside instructors to rent space. We have a huge main floor, another about half its size, and several small teaching rooms. If you're interested, email me and we can discuss it (I work there, but would have to talk to the owners and manager to really work something out for you.) Website is www.sacdance.com