I really wouldn't worry too much about a breakdown; the cars are pretty new.
If the car truly breaks down, I would think
Alamo would get a car to you. On your contract there's an Alamo service number you can call if you run into a problem. I actually did this last year because of a Check Engine light that was on and I wanted to know if they wanted me to keep driving it (turns out whoever had it last didn't screw the gas cap on). They said as long as I thought it was running OK to keep driving it, otherwise, I could take it back to MCO (I asked if I could take it to CCC and they said no...so I didn't bother)