I was in Vegas this past July & my parents have been twice this year (they go at least once a year). As cuterlt mentioned, there's a monorail from Bally's to MGM. A lot of Dis fans may know this - it is an old WDW monorail (Mark IV model). DW took my pic in front of it while there & the employees around us just kind of looked at us funny.

Sadly, it didn't have the "Please stand clear of the doors..." speil. Oh, well....
There are all kinds of free shuttles you can take. Harrah's has one that goes to Rio & back. There's one at Barbary Coast that goes to Gold Coast (next to Rio & across from the Palms. Gold Coast has a jazz band that plays daily for free & they sell 75 cent hot dogs). Behind Harrah's you can pick up a shuttle to Sam's Town and back. From Sam's Town, there's a free shuttle to downtown (Freemont Street).
We saw EFX Alive at MGM. It wasn't as much as the other shows, but was quite entertaining. I would highly recommend it. Rick Springfield is the star of the show (Tommy Tune was there before him). Be sure to get there 30 min early & watch for Sal.
If you're looking for daytime shows, Harrah's has a magic/comedy show by Mac King. You can get 2 for 1 or free tix to it. At Rio, Ron Lucas has a daytime ventrioquist show (same thing for tix). As you can tell, I did a lot at Harrah's & Rio. We stayed at Harrah's & had a *great* time.
There's plenty of other things to do out there. It's just a matter of looking and seeing what you have time for (Mirage has the volcano, Treasure Island has the pirate battle, several anamatronic statue shows in the Forum Shops at Ceasars, Aladdin has an indoor rain shower/show, etc. Be sure to look at the roof/sky in the Forum Shops. It shifts from day to night in the time frame of an hour or so).
No matter what you do, I'm sure you'll have a *GREAT* time. Just seeing the lights & scale of everyting there is amazing!! Have fun!!!
