I would agree with photographyxfactor, find a local community college or technical school in your area and see what they have to offer. A lot of the colleges where I live give weekend courses, a few Saturdays in a row (full day) or a couple of evenings a week over a couple of months. These courses are often at the introductory level and some even give advanced courses, once you have finished the introductory level one. If you don't have access to "college or tech school", then something like linda.com is a good bet. In your case, I suspect that the real thing you need is just a few introductory sessions and then you can proceed from there with a good Photoshop book.
If you don't need all the bells and whistles that come in CS5 (and its price) and most folks starting out do not, then you may want to look at its Cousin Lightroom, or at its lesser child Photoshop Elements. I have CS5 and Lightroom and I find that most of my editing/post-processing can be done in Lightroom, leaving the pixel-level tasks for CS5. My 0.02¢ FWIW.
Cheers,
WesternGuy