You can run it (I've never run it personally on a Mac), but due to the Intel processor switchover that occurred a few years ago, Adobe CS2 can't run natively on your Mac, and will have to be emulated using built-in Rosetta technology. This means you'll notice slowdown when running it, and other people have said there are some bugs that occur.
While CS2 will certainly work, if you're serious about running the Adobe suite, your best bet would be to get CS3 for Mac, which supports the Intel processors fully.
>I thought that the intel based macs (towers or imacs) just came out in 2007,
>maybe late 2006.
The transition to Intel processors began mid 2005, and was completely finished by the end of summer 2006.
>So.....Rosetta tells the machine that older software is running, but can make it slow...?
Sort of. Pre-intel Mac software was coded for the PowerPC processor. These binaries cannot execute natively on a different architecture (Intel), so an emulation layer is necessary. This emulation layer creates a virtual PowerPC processor which in turn executes the PowerPC binary. However, this extra layer slows down overall performance and is more bug-prone.
I vote either don't use CS2 or click [command] [S] often.. I was lucky to keep it running on a MacPro for more than 45min at at a time. It can depend on the size of the project though, mine were large PS documents several thousand pixels wide in RGB color.
Word has it that PowerPC code from Leopard will be largely eliminated in the upcoming release of Snow Leopard. Whether this includes Rosetta or not isn't certain, but I wouldn't be surprised if Apple ditched it. It's actually kind of disappointing how quickly Apple is trying to drop support for the older PowerPC Macs.