check on the prices both on dollar and national - they are generally cheaper than budget (so much for budget....)
also if you do get a deal with budget - their policy is different. I like economy cars - gas mileage over comfort for me. Anyway with the others I had to take what they had (generally not an economy). With budget I had to wait (with several other people) because they had run out of my type car - we waited at least 2 hours for it to bring in more cars. I won't use them again.
believe I have done offsite - Alamo, Hertz,
Avis - they are only a few minutes (generally under 10 to 15 minutes) - I will do them before budget again.
the problem I have with offsite is some little thing is wrong with the car. Well I have these things marked on my rental agreement. but sometimes the person you bring it to will argue with you anyway.....
Also my last time to use Alamo - the gas gauge was broken. I had a very difficult person - to try to force the poor car to take more gas. then he went and got a repair person - I told them both I have filled it up about 3 minutes before I returned it.....Anyway they both tried for over around hour and half to get the poor car to take more gas.....I also pointed out that the gas gauge was broken when I rented it (It was a older model.....) I should have complainted to Priceline about this but I didn't.
I always allow 3 hours to get to the plane - so in those days I was safe.
I would definitely leave enough time to have problems and then get to the airport - if you rent from offsite (or even onsite).
See why I drive my own car to Orlando - less trouble all around!!!!