MCO...there is no question.
my best deals on cars is with dollar unless i want some miles. sometimes you can get less than 20 a day.
daytona is a little spring break looking and biker (last i was there was post the few huricanes in 2005). I think Cocoa and Melbourne, as far as beaches go, are a little better. You can even try to plan for a launch in the Cape. St. Augustine is really nice and if this is the case, fly into JAX. some great seafood near the coast. The cape is a very short drive from MCO.
the one thing I did not appreciate in FLA with the beaches is the whole concept of the sand bars etc.
BTW, Flagler beach was the best we stopped at on our drive from YYZ. some some dolphins in the am. beach was close to the city etc. I think we even drove pretty far along the 1A too.