Hi, I was randomly looking at the SDSU community and saw your post. I'm in the molecular biology program at SDSU but it has a lot of overlap with the microbiology program. In fact the professor I work with pretty much does microbiology. I think the application process for both is the same, you just check the "microbiology box" instead of the "cell and molecular" box on the application. I started in the fall of 2008, so I'm still in my first year of the program. I did not go to SDSU for undergrad, I went elsewhere. I also was out of school for a while before I went back.
I found applying via the csumentor website to be pretty easy. There was a secondary departmental application but it was no big deal as I recall.
What kind of stuff did you want to know? I'd be happy to answer any questions you have about the program.