You can learn to sketching on their own (for example, as Hussein Al-Attar). Many of the world-renowned colleges do not teach drawing
. Colleges mainly provide the motivation, competition, contacts with employers.
The most important for you - learn to draw perspective and volume. Start with this tutorial: http://forums.sijun.com/viewtopic.php?p=272300
Try as much as possible to draw a pen and pencil. Do not use a computer and do not paint the sketches before you can properly draw the "frame".
You should draw a few hours a day. Next it will be easier.