had the same problem on my new hp 7520: No option to select the photo tray in Photoshop Elements 10 on my MacBook Pro (OS 10.6.1).
The solution was to use a preset generated in the seperate program standard on the Mac, Preview. The preset causes an additional window to pop up when you press print, and allows you to select the preset. You don't see this window unless a preset has been generated.
To set a preset in Preview follow these steps (other programs could probably be used to set the preset as well):
1. Select a photo and select print.
2. In the print screen select the paper size (eg. 4x6), then in the option that says preview use the drop down menu to select "printer features" which then brings up the options that we are looking for. Set the paper type (eg. Hp premium papers) and source (photo tray). Now go back to top and in the preset window select "save as" and give it a name (eg. 4x6 photo tray). This has created a preset with specified paper quality, size and source which can be used in Photoshop.
Once the preset is established you can easily print to the photo tray from Photoshop:
1. Select a photo and select print.
2. Select the printer, paper size and print size (should match preset) and select print.
3. Because of the preset, an additional window pops up allowing you to select the printer and the preset, then select print again to send it to the printer.
Of course you can have a number of presets, for different sizes or types of papers, different source trays or even different printers.
