If you have NEVER worked on Photoshop before, the best would be to first get ur hands dirty with online tutorials and get yourself familiar with the menu's and just the basic working of the software. Youtube is the best source.

Problem with going for short courses is that they just skim through everything quickly giving u an introduction, showing you what the menus do and other such options nothing useful..all of which you can learn online for free. Once you feel you are good with the basics just enroll yourself for more advanced course where you will fully unleash the power of Photoshop...thats just my opinion for value for money. :P