You can try to work something out with a Hertz Local Edition or with an Enterprise. Rent off-airport so you don't have to pay higher airport taxes. There are also CDP's out there that waive the under-25 rental fee, so be aware of those.
Keep in mind with this economy, you can probably buy a piece of junk commuter car for under 1000 bucks and just get liability insurance on it & get AAA for a year.