We've used Allegiant several times in the past couple of years. We always rent a car, watch the rental sites for the almost daily changing rates to get the best rate. I've never paid more than $80/week for a rental at SFB and usually less.
SFB is a nice small regional airport, no waiting in holding patterns to land, straight off the plane and down the escalator to baggage claim carousel, then out he door and across the street to the rental car lot. We have been leaving the rental car lot within 10 minutes of de-planing on several occasions. Definitely recommend the airport for the ease of arrival and departure due to it's smaller (and less hurried) size.
Once out of the airport you can head out on Lake Mary Boulevard to I-4 and then follow the signs southwest to Orlando and WDW (this is my preferred route, but I don't mind interstate traffic). Takes about an hour, a little more if you run into rush hour traffic.
Alternately if you want a quieter, more civilized drive to WDW then take the toll road SR-417 (I believe it's called the Central Florida Greenway). Traffic is lighter and it skirts around the outside of Orlando so the scenery is a little more soothing. I think we paid $5-8 in tolls when we used it a couple of years ago, probably a little more now. Takes a little over an hour to WDW.
Hope this helps with your decisions and have a nice vacation.
PS: watch out for those baggage fees and factor those into the cost of the trip. My advice here is pack light. We used to pack for every possible contingency and ended up lugging heavy suitcases everywhere and not using 50% of what we had brought.
On our last 2 week vacation the DW and I packed a weeks worth of Florida weight clothing each into ONE checked bag and took 1 carryon and my laptop bag (wore a light jacket and jeans onto the plain, to be used during our vacation in case of a cool evening or rain showers). We had a rest day after the first week at the parks and did a couple of loads of laundry at the resort while having a few cocktails and sunbathing around the pool, popped into town to restock our drinks and munchies stash and had supper off resort. Worked out great and we were ready for another week of park hopping etc.
