Good luck, I was in your same position when I was deciding on a manual or auto 370Z. I could not find a place that rented manual cars in IL; I even checked moving truck rentals & posted on craiglist. I ended up taking my Dad with me to a private seller with who had a manual 370Z I was really interested in. He let us take it out and my Dad drove to an empty school parking lot & we switched spots.
I did have dirt bike / motorcycle experience so I had some experience with a clutch and how shifting should work in general. That said, I "learned" how to drive a manual transmission in that car. Ended up purchasing it so I don't feel bad that I "used" his car to get the basics down. My suggestion would be to find the car you want in a manual version and give it a go. Depending on how serious you present yourself to a dealership, they may let you "learn" in the car.