No, I probably wouldn't do it. I'd be too nervous about cutting it that close. MCO has a strange(to me at least) way of handling luggage check in. 1st you have to wait in line at the airline desk to print up tixs and get luggage tags on. Then you schelp all your bags over to security, wait again, and then actually turn them over to be checked in. Also, I've noticed the lines at security check in can get pretty long. Asked a TSA agent nearby and he said there usually pretty long between 9 am and 1pm.
You'll be storing your luggage at front desk, relying on the buses, and having to go back to pick up luggage. If you had a car, you might be able to do it, cause then you could go straight to the airport. BTW, how are you getting to the airport with no rental car?
Guess I'm just a nervous nelly, but it would be too close for me to do it.