Hi Glauco,
I recently had a rails project where I needed the same thing. My text was in a helper module, but I added
# encoding: UTF-8
to the top of the file and it worked.
You would need to add a
<%# encoding: UTF-8 %>
to the top of your view file. If you use it in multiple views, you might can try adding it to your _layout file (I haven't tried this part, but I confirmed that the line in the view file works). Interesting note, for others reading this: if you're using haml views, this isn't necessary. They must handle the encodings.
As for the images, I actually wasn't aware of the image helper. I use the image_tag helper (same as in rails) there you can pass the format <%= image_tag("/images/image_name.jpg") %> Unfortunately you do have to pass the /images directory in the pathname.
Hope that helps, let me know if you run into any issues.
Jess