Unfortunately "Scale to Fit Media" isn't a toggle. But let's try a workaround.
You can create an Image Size action where you will scale the picture to either 8.5 inches wide or 11 inches high, whichever works best for you. First be sure "resampling" is turned off under Image > Image Size.
You would open an iimage, then create an new action, title it "Letter 11 inches" and that's when the recording starts.
Enter 11 inches as the Height, click OK and then stop recording.
This is a quick and dirty action and assumes all pictures are portrait and not landscape. It may just work for you.
You should be able to include it in your batch processing.
Hi Spill, I had the same exact issue. It's a pain to have to check that scale to fit every time.
Unfortunately I haven't found a solution for changing this to a default. But here's what I have been doing as a work around.
In my workflow, I save images as .PSD files. Then I select all the images in finder and open them with the Preview app. Sometimes multiple windows appear, but usally most of my images are in one preview window. Then when I saw file -> print I have the option to scale to page, and it is printing 190 files instead of individually.
Now, obviously this only works if you're using a Mac. But maybe there is a similar solution on PC.