DPI is meaningless in shooting digital images. What is important is the total resolution:
In your case, 4272 x 2848, give or take. 
Canon's Digital Photo Professional has a setting that seems to do what you want. Use "Batch Process".
There is an output setting there, but I have never used it
The question was, "How do I change settings on my EOS Rebel T1i so that my photos are 300dpi?"
What you displayed is "print settings". There is no 300 dpi in the camera. Print settings are entirely a different thing.
The top red circle deals with the image size. The bottom blue circle deals with print size. Two different quanties. DPI can only be set as an output from an editor.
I think you are confused a bit.
The resolution of a RAW file and a JPEG is identical unless you scale it up or down. Processing a RAW file does not affect its resolution. There is no DPI involved. If you save it as TIFF, you can get the same color-depth too. If you save it as JPEG, then the bit-depth reduces to 8-bit per channel.
A digital image is composed of pixels. Each pixel represents one colored dot. Millions of pixels make an image. The term resolution is frequently used to describe the number of dots that make up that image. Photoshop calls it the image size because it uses the term resolution to describe it. But resolution does not describe the physical size of an image because the size of each pixel is not known, just how many there are.
Thet digital cameras produce images of a given number of pixels, but what is the resolution of the camera's image? The real answer is that it depends on the viewing or the printing size. Software cannot tell what the true DPI of an image is without additional input from you. This is where software like Photoshop confuses folks. Photoshop assumes a DPI until correctly input by the photographer. To do that you access the resizing box or tab, and change the DPI. Now with the resample option unselected Photoshop knows that it must not change the image's pixels in any way. It simply sets the DPI. Once the DPI of an image is set, the software knows its intended physical size. Photoshop can figure out the correct DPI by asking the person for a physical size.
Any number of images sizes can be selected and Photoshop figures out what DPI is required. Remember that physical size, image size and image resolution are related, so if any two are known, the third one can be figuered out.
Once an image's DPI is selected, it can be printed easily to a specific size.
To further this discussion, where do you find DPI in Photoshop? If you notice the example I displayed says PPI or Pixels Per Inch. Not DPI or dots per inch. Which is undersdtandable as DPI is a PRINTING term and not a digital image term.
