In my experience, the expos at DL have been much more laid back...still get crowded, but never seem to be as completely nutty as the PHM expo.
As for the busses...on race weekends at WDW the event busses are separate from any of the regular park busses...usually are the big chartered busses and are marked as runDisney event busses...they will only be going from resort to expo and back or resort to race and back. There are always taxis hanging around WWoS though...you could grab one of those directly to a park from the expo. Honestly, I've started using them more and more to and from the expo in the last year or two just because it ends up being so much faster...for me, any extra time I can get off of my feet and not standing in a line the day before a race is totally worth the cab fare