I think the Lobby Bar in the Luxor has free Wifi. If you have a car there is a Starbucks near the outlet mall at Windmill and Las Vegas Blvd. There is also the Enterprise public library on south Las Vegas Blvd.
There's a food court on the casino level of the Venetia that usually has good, free wifi. You can also pick up free wifi near that Apple store in the Fashion show mall. Those are your best bets near the TI.