> It'd probably take a couple hours to walk between Mandalay Bay and Encore

I've only done that particular walk once, but walking from Tropicana to Encore (a bit farther than Mandalay - Encore) took about 45 minutes I believe; a bit of a trek, but definitely manageable.

I think in an entire week on the strip, I took a cab exactly twice; once from the airport to the strip, and once to a shopping mall off the strip. Had Uber been around when I was there, I certainly would have used it more.