At least 20 minutes, given that it's through a casino. With you probably carrying a backpack full of conference swag.

And that's from the front entrance -- not counting getting from one hotel to another.

I've gone to dozens of conferences in Las Vegas -- so much so that I know the name and location of the meeting rooms in many of the hotels. I can compare that to attending several dozen conferences elsewhere, from Hanover to San Francisco to Orlando to ohgeez so many other places. Las Vegas has benefits, but the travel issues cause me to ALWAYS stay at the conference hotel whenever possible.