You could help KKK, dunno though, that might be a stretch to ask though.
if you are willing to pay a fee, then there are casinos all over town that will host a good MM watch party. steve dave mentioned one of them (i didn't go last year because it took me too long to register), but there are dozens. here are some of them:
http://www.vegaschatter.com/story/2013/2/14/133253/571/vegas-travel/VegasChatter's+Guide+To+March+Madness+Partiesthe LVH theater is a great place to watch and is also free. but as you might expect, it will fill up extremely fast, so would need to get there extremely early and probably even wait in line for a few hours. if you plan to watch at a book, the further away you are from the strip, the later you can show up to get a seat. good off strip options include South Point (they'll open up second floor ballroom), Green Valley Ranch and Red Rock. Sunset is also a decent book with adequate seating space.
if you plan to watch at a sportsbook, avoid all cantor books - located at palazzo, venetian, The M, cosmopolitan, palms and tropicana. you have a 5% chance of finding a seat and a 0% chance of getting a free drink.
other books to avoid:
-caesars (awful TVs; can't see unless super close)
-MGM/Mirage (currently remodeling; not sure if it will be completed, but it wasn't close to done the other day)
-bellagio (overrated book as it is, no longer gives away free drinks)