Keyboard Shortcut for Navigating to a Text Field in Google Chrome
Install the Vimium extension for Google Chrome.
Usage
Type f and all controls and links get a letter combination; here an example for the www.google.com page:
Now type n to put the cursor focus in the text field; n because that's what Vimium assigned to this particular textfield.
That's it.
With the Vimium extension, you can use the command gi to focus the first (or n-th) text input box on the page.
Natively there's no keyboard shortcut to do this, so I fear there's no real solution for this.
What you could try is write a Sikuli script to look for text boxes and then make it mouse click in it.
However, this would only work if the textboxes are similar to the one you use in your script.