How to learn OpenGL ES 2.0 without any previous experienced on OpenGL

Hi everyone!

The first time I attempted to use OpenGL ES 2.0 is when I doing a Android tutorial on the official Android developer site (Couldn't paste the link here due to limitation of the first post). It is really cool to add some graphics/animation to your app and I think I will spend some time to learn about this. At that time I still thought I am a quick learner and I was wrong.
I could not mapping the pixel on the phone screen with the [-1 1] coordinating system of OpenGL after days of Googling and hoping for some detailed tutorial online. The way the library is used also strange me in several points (yeah, I'm not quite an experienced developer). For example: we have to write the code for the shader (C++ code I think) in a string! And the way we access to "program" and its components through a integer by calling is really make me think why the API is so complicated.

I would really love to have your advices on learning OpenGL (specifically OpenGL ES 2.0). If your method was Googling, I hope that you can point me to some good sites.

Thank you,