From Episode #83, The Case of the Prudent Prosecutor
Saddle Peak Lodge
DVDs do make a difference. It appears that the opening scene takes place at the Saddle Peak Lodge at 419 Cold Canyon Road in Calabasas, California.
From the DVD. The sign is readable on video tape if you know what it says.
The name is on the door sign too.
A close-up of the door sign.
For a change, the address is not that of the studio where the show is filmed. This address is likely in Ojai, California, about 56 miles from the Lodge as the Google maps.