Only day of ALCO options:
Blue 7G - only allows 20 day-of without a pass.. unless you get there over an hour before it opens.. you aren't gonna be in that lot $35
Blue 7J - allows 90 day-of without a pass.... get there a little early, or certainly not much later than when it opens and you will probably get a spot in there $35
Blue Canal Lot - lots of spots available without a pass.. $30
All allow tailgating.. bule 7G and 7J are under the overpass, which is nice becuase if it rains you aren't getting wet.
All the closer lots are all pre-sold with passes....
I don't know anything about any of the non-alco lots, like the Science Center.
here is a map:
The information sheet says 7G and 7J are pre-sold, but I know personally that they allow 20 and 90 respectively.