I go to the Chicago auto show every year, hoping to get some buddies from Cincy to go with me again this year.
I love using the 10-22mm EFS at the autoshow, but it's not my most used lens. Because of the wide angle effect many of the cars just appear too distorted.
I use an 18-xx zoom most often. I used a Sigma 18-125mm DC in the past most often, last year I only carried my 17-40L with me. It's some what dark at the auto show so I usually use ISO800.
I have a new 17-55mm EFS now so that will be my new go to lens, but the 10-22mm will be in the bag nonetheless.
I would lean harder toward selling the 28-135mm for a wider zoom like the 17-85mm EFS IS or Tamron 17-50mm.
Else if you have the money I would look toward adding a Sigma 10-20mm or Tamron 11-18mm to complement the Canon 28-135mm in a 2 lens kit. Else if you have the cash go for the Canon.
Adding a cheap 18-55mm IS f/3.5-5.6 to the 28-135mm would be a great alternative for the autoshow IMO.
I like using lensprotogo.com for my lens rentals when I do rent a piece of glass. The 28-135mm IS EF is a nice lens I wouldn't sell that lens unless you find the 28mm end not wide enough for general use.