Just look for the 70,000 square foot white circus tent, surrounded by hundreds of RV's that are surrounded by hundreds of swap meet style booths selling everything under the sun.
During the RV show run, which is January 18th thru the 26th, downtown can get pretty backed up. It is easier to enter/exit from the east or west off of I-10 as all of the 95 traffic has to flow through a single intersection that quickly becomes a choke point. We have seen it backed up both north and south for more than a mile. :S
We like to arrive on Monday and settle in over at Scadden Wash and then hit the show when it opens at 9 on Tuesday morning. By 11 the tent is beyond packed and we retreat back to our campsite and return in the mid afternoon around 3'ish and the crowds have usually thinned considerably. A couple of days and nights is about right for us but many stay for much longer. You might not want to go twice but you gotta see it at least once. :B