OK, here is how to do the L without bothering with busses:
Buy a $ 3.00 transit card from the CTA machine at ORD (just before the turnstiles).
The one way fare is $ 1.50.
Take the Blue line L train to the Washington Street stop (this follows Clark & Lake Streets).
On the platform, look for the stairway that goes DOWN and is marked for passage to the RED LINE.
Go down the stairs to the pedestrian walkway and proceed 1 block to the next stairway at the end of the tunnel. Don't even think about trouble since there are dozens of others there all of the time.
Go up the stairs one level to the RED line. On the platform, board the NORTHBOUND train headed to Howard Street or Evenston.
Exit the Red line L at Addison Street and you are a block from Wrigley Field and can follow the crowd there.
The same fare card will take you home and use up the balance of $ 1.50.
The total trip (one way) should be about 75 minutes.
After the games, there is often a line to board the Red line (southbound) but you should be able to get on by the third train or so.
And don't worry about creeps on the CTA. I have done it many, many times without problems.