Taking public transit to Levi’s Stadium is the way to go. Travel by Caltrain down the peninsula to the Mountain View Transit Center if you are coming from the north. Once there you can hop on one of the buses waiting or just ride the VTA Light Rail for about 30 minutes and you will be dropped off right outside. (Upon leaving the Stadium, just return to where you were dropped off). Waiting lines and destinations are clearly marked and the VTA light rail trains run every 15 minutes during game day, so the wait is minimal. Buses get there a little faster with fewer stops but do not leave until they are full.
This does not seem to be an issue as throngs departing from arriving Caltrain trains quickly fill the buses. When taking the light rail, purchase an 8- hour excursion pass at the ticket vending machines and this will allow you a one stop option for the return trip. The cost is $4.00 and avoiding the traffic woes makes it worth every dollar. The new stadium is very unlike Candlestick Park, especially the weather. The Sun is out in force as are the 49er Faithful, so just be prepared, put on sunscreen and enjoy the game. Please be aware of the “Bag” policy for the NFL.