I live in Arcadia, about 5 minutes east of Pasadena (the Rose Bowl) off the 210 freeway.
From my house, its 1 hour to San Manuel (look up the web site for all these Indian Casinos), straight down the 210, and can get very crowded because its the closest to LA.
Morongo is further east off the 10 freeway, about 1-1/2 hours.

Pechanga is 1-1/2 hours down the 15 freeway, south-east towards San Diego and is one of the nicer ones.
Add another 1/2 hour to get to Pala or Harrahs in the same area, but you have to take windy back roads.

You also can go west from Pasadena on the 101 freeway, at least 2 hours to Chumash, past Santa Barbara.

Let me know if you need better directions.
Check their web sites for day buses; Harrahs has a free one, usually picks up around 7:30-8, arrives there around 10, leaves around 3, and gets back around 5:30-6p.