Julie,
This bothers me when I am on the road, however, the inns are filling their rooms with two and three night stays so they do hesitate booking one night and leaving the room empty two nights when they can get a guarantee booking for two or three.
The only suggestion I can make is to call a B&B you are interested in, explain that you are "on the road" and only require one night. If they have more rooms open then booked, they may accommodate you. Some inns will tell you to call back a couple of days before and will take one night bookings after Thursday. I suggest that you check the places on line that you are interested in and since more and more inns are doing on line availability, you can save yourself some phone calls if you see the inn is already booked for the weekend.
You can also check bedandbreakfast.com's hot deals every Wednesday (after 10:00 am mountain time) to see what inns are offering in the way of discounts for the coming week. In order to be listed, inns must offer at least a 20% discount and oft times will drop the two night minimum for last minute bookings.
I did do some research for a guest once about a year ago on this same topic and at that time the Candlelight Inn in Napa showed one night availability for several Saturday nights. I just did a quick availability check for a couple of upcoming Saturdays, July 22nd and August 5th for one night and two rooms were available on each of those dates.
http://www.bedandbreakfast.com/california/candlelight-inn.html
I hope this helped a little. Rose
Rose Ciccone
Mail To: roseciccone@verizon.net
Associate Editor - BedandBreakfast.com Report
http://www.bedandbreakfast.com/report/Spring-06/index.htm
Contributing Editor - America's Favorite Inn's, B&B's and Small Hotels
Rose Ciccone
Mail To: roseciccone@verizon.net
Associate Editor - BedandBreakfast.com
http://blog.bedandbreakfast.com
http://www.bedandbreakfast.com/report/Fall-07/index.htm