Ok, Carlos, glad you asked, and I’m up for the challenge!  I’m going to use Orlando as a test case, because I personally always have Walt Disney World in mind!  Since you didn’t mention, we’ll go with Orlando for now….  I’ll check a few prices for you real quick!

First let’s try Priceline:  See Winning Rental Car bids in Top Cities from $12/day!  When I clicked on this link it took me to the Priceline auto rental site, and a map of the United States was shown.  When I moused over the state of Florida, I was able to see that Orlando was displayed, so I could see the winning bids for car rentals in Orlando.  A mid size car winning bid was $17.00.  This is less than your budget of $50. a day, so Priceline would be a good place to try for cheap auto rental.  The next step would be to click through that page on the Priceline site, and go to “Name Your Own Price.”  And since you know that others have won bids for $17. you could try that price and see if you get a match.  You may have to try a couple of times, since you’re looking at a holiday season.  I’ve used Priceline quite a bit for hotels near LAX, Los Angeles Airport, and got great rates, and great service. 

Travelocity has an auto rental ad that sounds great!
Car_Renting a car just got easier! Return your vehicle as is and pay pump prices for gas!
You have a choice of auto rental companies, and the price is between $107. and $112 per day, and I did use your dates of December 26 – 29, 2008. So the prices may be a bit high due to the holiday.

So – If I were in your shoes, Carlos, and I needed to rent a car in Florida for just after Christmas, I would book ahead, and I would first try to name my own price with Priceline. Since you actually have to enter your credit card number to see if you win your bid, I wasn’t able to get a final price for you. But since you actually need to book a car, you might want to follow through the links with Priceline and see if you can win a bid. If you haven’t tried it before it’s not hard. You will need an email address (which you have) and a credit card.

Good luck and let us know how it turns out! I have a few other discount sites I can check too, if you don’t get a winning bid under $50. with Priceline – just let me know and I’ll dig around a bit more!